Treatment of stereotypic, self-injurious and compulsive behaviors in man and animals using antagonists of NMDA receptors

Abstract

NMDA receptor antagonists can be used in methods of treatment, for reducing the frequency of stereotypic behaviors in animals and for reducing the frequency of analogous compulsive behaviors in humans, for example, those that have been said to be a manifestation of, or related to, obsessive-compulsive disorder. Of particular interest is the non-competitive NMDA receptor antagonist memantine.

Description

BACKGROUND OF THE INVENTION

Stereotypic behavior in animals (also called “repetitive” or “compulsive” behavior) has been defined by some researchers as acts that are repetitive and constant, appear to serve no obvious purpose, and may even be injurious. One of the most common of these behaviors is, for example, crib-biting by horses—grabbing and biting of the feed bin or of parts of the structure in which the horse is housed (also called “cribbing”—see U.S. Pat. No. 4,692,451 for a description of this behavior, associated behaviors, and resulting problems). Another common behavior in dogs is compulsive licking of itself—even to the point of aggravating a sore (“lick granuloma” or “acral lick”). Stereotypes may show some degree of variation, and may be unlike the more typical behaviors such as cribbing and licking, in that they have no features of repetitive motion, but are characterized rather by motionless staring or a frozen body position.

The repetitive behaviors of animals and the compulsive behaviors of humans have both responded to treatment with some of the same drugs. See, e.g., regarding treatment of acral lick with drugs that have shown benefit in human obsessive-compulsive disorder (OCD), Rapoport, J. L., Clin. Neurophar., 15:Suppl. 1 Pt A:261A-262A, 1992; Rapoport, J. L. et al., Arch. Gen. Psychiatry, 49:517-521, 1992. See also Smith, K. C. and Pittlekow, M. R., J. Am. Dermatol., 20:860-861, 1989, wherein it was reported that onychophagia and skin picking responded to treatment with (−) enantiomers of opioid antagonists, which have been effective also in compulsive hair pulling in cats, feather picking in birds, acral lick in dogs and cribbing in horses (Dodman, N. H., Vet. International 6:13-20, 1994; Dodman, N. H. et al., J. Am. Vet. Med. Assoc. 193:815-819, 1988; Turner, R., Proceedings of Annual Conference of the Association of Avian Veterinarians: Aug. 31-Sep. 4, 1993, Nashville, Tenn., pp. 116-118). See also U.S. Pat. No. 4,692,451, the contents of which are incorporated herein by reference in their entirety. Studies of this type provide justification for the conclusion that the same underlying physiological processes are involved in causation of the animal and human behaviors. Therefore, they should all respond positively to new methods of therapy.

SUMMARY OF THE INVENTION

The invention relates to a method for treating a disorder in animals, variously termed repetitive, stereotypic, or compulsive behavior, and which can also be self-injurious, by administering to the animal, by one or more appropriate routes and by appropriate doses, an effective amount of one or more NMDA receptor antagonists. A particularly preferred NMDA receptor antagonist is memantine. In some cases, the composition comprises one or more NMDA receptor antagonists that are not haloperidol. In some cases the composition comprises one or more NMDA receptor antagonists and does not comprise an opioid receptor agonist or antagonist which is primarily (−) enantiomer. In some cases the composition comprises one or more NMDA receptor antagonists but does not comprise an opioid receptor agonist or antagonist of either (+) or (−) enantiomer.

The invention, more particularly, is a method for treating compulsive behaviors in horses, such as crib biting, wind sucking, stall walking, weaving, head bobbing, pawing, tonguing, self-biting, flank sucking, and head shaking, by administering to the horse a composition comprising one or more NMDA receptor antagonists.

In another particular embodiment, the invention is a method for treating compulsive behaviors in dogs, such as compulsive licking (acral lick), tail chasing and whirling/spinning, pacing, fly chasing, shadow or light chasing, excessive barking, stone eating, excessive drinking, and excessive eating, comprising administering to the dog an effective amount of an NMDA receptor antagonist.

Also an embodiment of the invention is a method for treating compulsive behaviors in cats, such as wool sucking, compulsive licking, tail chasing, hoarding, pacing, excessive marking, compulsive masturbation, and compulsive aggression.

A further embodiment of the invention is a method for treating compulsive behaviors in birds, such as feather and skin picking.

The invention relates to a method for treating a disorder (or more than one disorder, as it is possible that two or more can occur together) in humans, variously termed repetitive, stereotypic, or compulsive behavior, and which can also be self-injurious, by administering to the human, by one or more appropriate routes and by appropriate doses, one or more NMDA receptor antagonists, thereby relieving the frequency and/or intensity of the compulsion and reducing the frequency and/or intensity of the behavior.

Examples of the human behaviors which can be treated by these methods include, but are not limited to: obsessive-compulsive disorder (with its various manifestations of checking, counting, washing to remove contamination, etc.), trichotillomania, psychogenic excoriation, nail biting, compulsive exercising, smoking compulsion, compulsive overeating (often leading to obesity), drug (opioid) addiction, and alcohol addiction. These compulsive behaviors may be related also to compulsive gambling, compulsive shopping, anorexia nervosa and body dysmorphic disorder.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph in which cumulative crib-bites per time after administration of (+)-methadone (diamonds), as well as the rate of crib-bites per 5-minute interval (squares) are plotted, showing the effect of (+)-methadone on the rate of compulsive crib-biting in horses.

FIG. 2 is a bar graph in which the cumulative number of turns of the stall in 30 minutes are plotted for a stall-walking horse observed before and after the injection of dextromethorphan. Dextromethorphan-HBr, 1.0 mg/kg i.v., was injected after 30 minutes of control observations. “Saline” indicates the number of turns by the horse, observed in 30 minutes after injection of saline. “Dextro” indicates the number of turns by the horse, observed in 30 minutes after injection of dextromethorphan.

FIG. 3 is a bar graph showing the time spent in three typical behaviors in four experiments in which the effect of dextromethorphan on a shadow-chasing dog was tested on four consecutive days. Back slash hatching indicates “searching”; forward slash hatching indicates “fixated”; white indicates “resting.” Dextromethorphan-HBr, 2 mg per kg p.o. was administered twice daily, and testing was carried out one hour after the morning dose. Bars indicate the total time of each of three behaviors during the first 10 minutes after the beginning of testing. Time not accounted for was spent in moving about the room, usually out of range of the camera.

FIG. 4 is a graph of the cumulative number of scratches by a mouse, plotted at 10 minute intervals, when naltrexone (10 mg/kg; squares), dextromethorphan (10 mg/kg; triangles), or no compound (control; diamonds) was injected into the mouse 10 minutes before injection of compound 40-80.

FIG. 5A is a graph of the cumulative number of scratches by a mouse, plotted at 10 minute intervals, when haloperidol (2.0 mg/kg; triangles), dextromethorphan (20 mg/kg; squares), naloxone (20 mg/kg; diamonds) or no compound (x's) was injected into the mouse 10 minutes after injection of compound 40-80.

FIG. 5B is a graph of the cumulative number of scratches by a mouse, plotted at 10 minute intervals, when (+) methadone (5.0 mg/kg; squares), (+) methadone (10 mg/kg; triangles), or saline (control; diamonds) was injected into the mouse 30 minutes after injection of compound 40-80.

FIG. 6 is a drawing illustrating the structure of the compound memantine.

FIG. 7 is a series of graphs of the average cumulative number of scratches by mice, plotted at 5 minute intervals for 30 minutes, when saline or memantine (2 or 5 mg/kg) is injected into the mice 5 minutes prior to injection of compound 48-80.

FIG. 8 is a series of graphs of the average cumulative number of scratches by mice, plotted at 5 minute intervals for 30 minutes, when saline or memantine (2 or 5 mg/kg) is injected into the mice 5 minutes prior to injection of serotonin.

FIG. 9 is a graph of the average cumulative number of scratches by mice plotted at 5 minute intervals for 30 minutes when saline or memantine (15 mg/kg) was injected into the mice 5 minutes prior to injection of serotonin.

FIG. 10 is a graph of the average cumulative number of scratches by mice plotted at 5 minute intervals for 30 minutes when saline or memantine (30 mg/kg) is injected into the mice 5 minutes prior to injection of serotonin.

FIG. 11 is a graph illustrating the response of dogs having compulsive or repetitive behaviors to treatment with memantine.

FIG. 12 is a graph illustrating the reported relative change in the behavior of the dogs that responded to treatment with memantine.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to methods of treating animals displaying various types of repetitive and/or compulsive (frequently also called stereotypic) behaviors using compounds that are characterizable as NMDA receptor antagonists (having specific binding activity to NMDA receptors and/or the ability to block activation of the NMDA ligand-gated channel by an activating compound).

Compulsive or stereotypic behaviors in dogs can be put into several categories. “Grooming behaviors” can include, for example, lick granuloma (acral lick), compulsively licking objects, self-scratching, chewing feet, hair and nails, etc., flank sucking and air licking. “Locomotory behaviors” can include, for example, running and jumping, pacing, head shaking, paw shaking, tail swishing, freezing, whirling, tail chasing, walking in a pattern, as along a fence, digging and floor scratching. “Vocalization behaviors” include, for example, rhythmic barking, growling or snarling at self, barking at food, crying and howling. “Predatory behaviors” include, for instance, staring, air batting, jaw snapping, pouncing, prey chasing or searching, ducking, and fly chasing. “Eating and drinking behaviors” include, for example, excessive drinking, polyphagia, excessive drooling, gravel and dirt eating, stone chewing, wool sucking, and eating fabrics. “Sexual behaviors” include, for example, compulsive mounting and masturbating. See, for tables compiling the observed behaviors of not only cats and dogs, but also horses, primates and other species Dodman, N. H., “Veterinary Models of Obsessive-Compulsive Disorder,” Chapter 16, pp. 319-334 In Obsessive-Compulsive Disorders. Practical Management (M. A. Jenike et al., eds.), Moseby, Boston, 1998. See also N. H. Dodman et al., “Veterinary Models of OCD,” Chapter 6, pp. 99-143, In Obsessive-Compulsive Disorders. Diagnosis, Etiology and Treatment, (E. Hollander et al., eds.), Marcel Dekker, New York, 1997. See also Tables 1 and 2 in Luescher, U. A. et al., “Stereotypic or Obsessive-Compulsive Disorders in Dogs and Cats,” In Veterinary Clinics of North America: Small Animal Practice, 21(2):401-413 (March, 1991).

Cats can exhibit behaviors similar to those seen in dogs, with the most common behaviors being those related to grooming, such as excessive self-licking and hair chewing. Other repetitive behaviors are tail chasing, hoarding, wool sucking, pacing, excessive marking, compulsive masturbation, and compulsive aggression.

Horses have not been observed to display compulsive predatory behaviors, but can also suffer from species-typical compulsive behaviors, such as cribbing, wind sucking, stall walking, weaving, head bobbing, pawing, lip flapping/tonguing, head shaking, flank biting, trichotillomania, and masturbation.

Birds, especially those of the order Psittaci, which includes parakeets, cockatoos, lories, macaws, and South American and African parrots, are subject to compulsive behaviors, particularly feather pulling and skin picking, but also route tracing, spot picking, masturbation and regurgitation.

Compulsive behaviors exhibited by animals of the porcine species include bar biting, vacuum chewing, and chain chewing.

Animals of the ovine and bovine species can exhibit behaviors similar to those seen in other species. These include tonguing and compulsive sucking, weaving, hair licking, and masturbation.

Bears in captivity have developed pacing behaviors.

Primates in captivity have been observed to have the following compulsive behaviors: hair pulling and skin picking (categorized as “grooming” behaviors), self sucking, licking and chewing (“consummatory” behaviors), self-directed aggression (“aggressive” behavior), masturbation and rectal probing (sexual behaviors), and bouncing in place and somersaulting (locomotory behaviors).

Humans, as would be expected, have developed a great variety of compulsive behaviors, compared to those of the animals. Common human behaviors include: paraphilias (sexual); self-directed aggression and pyromania (aggressive); checking, avoidance of contamination (fear and avoidance); skin/nose picking, trichotillomania (grooming); gambling, hoarding (“predatory”); whirling, tics, compulsive exercising (locomotor); and binge eating (consummatory). This list, like the lists of behaviors of the animals given above, is not intended to be complete or limiting, as variations with each individual animal or human are possible. Further descriptions of human compulsive behaviors can be found in Diagnostic and Statistical Manual of Mental Disorders (DSM-IV™), American Psychiatric Association, 1994.

Stereotypic animal behaviors have been compared to obsessive-compulsive disorder and disorders involving similar repetitive or compulsive behaviors in humans. As Freud described compulsive behavior, “the patient is impelled to perform actions which not only afford him no pleasure but from which he is powerless to desist.” It has been hypothesized that a more satisfactory definition of stereotypes or compulsive behaviors would encompass both the animal and human syndromes, by being based on common, specific neuropathologic differences in the brains of animals or humans manifesting these behaviors, compared to animals or humans that do not manifest such behaviors. See discussion in Luescher, U. A. et al., “Stereotypic or Obsessive-Compulsive Disorders in Dogs and Cats,” In Veterinary Clinics of North America. Small Animal Practice, 21(2):401-413 (March 1991).

The similarities have led some to refer to not only the human behaviors, but also the animal behaviors, as “compulsive” behaviors or “obsessive-compulsive disorders.” See Overall, K. L., Canine Practice, 17:39-42, 1992; Dodman, N. H. and B. Olivier, CNS Spectrums, 1(2):10-15, 1996. It has been proposed that acral lick in dogs, and compulsive bar biting and chain chewing of tethered sows, as well as several other behaviors of animals, might serve as useful models of human obsessive-compulsive disorder (Dodman, N. H. and B. Olivier, CNS Spectrums, 1(2):10-15, 1996). Compulsive self-grooming behaviors in animals, in particular, have been compared with trichotillomania in humans (Moon-Fanelli, A. A. et al., Chapter 3, pp. 63-92 In Trichotillomania, (D. J. Stein et al., eds.), American Psychiatric Press, Inc., Washington, D.C. The serotonin reuptake inhibitor citalopram has been found to be useful in the treatment of OCD and possibly compulsive hair-pulling in humans, and has been used successfully, in the majority of the dogs in the study reported, to treat acral lick dermatitis (Stein, D. J. et al., Depression and Anxiety, 8:39-42, 1998). These data provide evidence that acral lick dermatitis can be a useful animal analog of OCD.

Similarities that can be observed among the repetitive animal behaviors, and between the repetitive behaviors of animals and the repetitive behaviors of humans, suggest a common etiology. In addition, there are studies that link one human syndrome to another. Neurologic disorders such as epilepsy, Sydenham's chorea, and toxic and vascular lesions of the basal ganglia have been found concurrently with OCD (Freeman, J. et al., Paediatrics, 35:42-49, 1965; Kettle, P. and I. Marks, Br. J. Psychiatry, 149:315-319, 1989), leading to the suggestion that repetitive behaviors may be a sign of acquired disease. Observation of increased rates of OCD in Tourette syndrome (TS) patients, increased prevalence of tics and TS in OCD patients, and the increased familial rates of OCD and TS in first-degree relatives of both TS and OCD probands lead to the conclusion that there is a genetic association between the two disorders (Leonard, H. L., et al., Am. J. Psych., 149:1244-1251, 1992; Leonard, H. L., et al., Adv. Neurol., 58:83-93, 1992). A study of the incidence of OCD in the first degree relatives of trichotillomania patients found a higher lifetime prevalence of OCD in this group than in the relatives of normal controls (Lenane, M. C. et al., J. Child Pyschol. Psychiatry, 33(5):925-933, 1992). Attention deficit/hyperactivity disorder occurs frequently with Tourette syndrome (see, for example, Harris, E. L. et al., J. Int. Neuropsychol. Soc., 1(6):511-516, 1995).

N-methyl-D-aspartic acid (NMDA) selectively activates a major subclass of glutamatergic excitatory amino acid receptors in the vertebrate central nervous system (CNS). The NMDA receptor is a ligand-gated channel that is activated by the coagonists glutamate (or selectively in vitro by NMDA) and glycine acting at a strychnine-insensitive glycine site (Wong, E. H. F. and J. A. Kemp, Annu. Rev. Pharmacol. Toxicol, 31:401-425, 1991). It is further subject to regulation by a voltage-dependent block of the channel by Mg²⁺, a voltage-independent action of Zn²⁺, the redox state of the receptor, arachidonic acid, ethanol, neurosteroids, pH and polyamines.

NMDA-sensitive ionotropic glutamate receptors consist of tetrameric and heteromeric subunit assemblies that have different physiological and pharmacological properties and are differentially distributed throughout the central nervous system. The NMDA receptors are positively modulated by glycine, by polyamines (spermine and spermidine), by histamine and, under some conditions, by cations. NMDA receptors are coupled to glutamate-gated high conductance channels permeable to K⁺, Na⁺, and Ca⁺⁺, that are critical for long-term potentiation, and are selectively activated by the artificial glutamate analog N-methyl-D-aspartate. There is evidence that NMDA receptors play an important role in learning and in other phenomena in the brain, such as drug dependence and addiction, chronic pain, and CNS development, as well as in normal or disturbed synaptic transmission in some areas of the CNS. See, for review on NMDA receptors, Danysz, W. and Parsons, C. G., Pharmacological Reviews, 50(4):597-664, 1998.

An NMDA receptor antagonist is any one of a number of agents which has been shown to bind to NMDA receptors and/or block any of the sites that bind glycine, glutamate, NMDA, ketamine or phencyclidine (PCP). Blocking the NMDA receptor sites has the effect of preventing the creation of an action potential in the cell. NMDA receptor antagonists include those compounds that preferentially bind to NMDA receptors, but may also have other activities.

NMDA receptor antagonists include the following: previously identified competitive and non-competitive antagonists of NMDA receptors, which may bind, for instance, at the glycine site (on the NR1 subunit) and/or at the glutamate recognition site (on the NR2 subunit). Preferred NMDA receptor antagonists are those that have the ability to cross the blood-brain barrier and also demonstrate a low incidence of side effects. Such NMDA receptor antagonists can include, for example, compounds known as arylcyclohexylamines such as the anesthetic ketamine and neuroleptics such as haloperidol (Coughenour, L. L. and J. J. Corden, J. Pharmacol. Exp. Ther., 280:584-592, 1997) and the anti-Parkinson drug amantadine. Enprodil and eliprodil are neuroprotective agents whose mechanism of action has been attributed to their NMDA antagonist properties (Scatton, B. et al., pp. 139-154 In Direct and Allosteric Control of Glutamate Receptors, Palfreyman, M. G. et al., eds., CRC Press, 1994). Trifluperidol and haloperidol have been shown to have a similar selectivity for the NR1a/NR2B receptor subtype expressed in Xenopus oocytes (Ilyin, V. et al., Soc. Neurosci. Abstracts, 21:835, 1995. Memantine, felbamate, ifenprodil, eliprodil, CGS19755, remacemide, and CNS 1102 are also antagonists of NMDA receptors (Lipton, S. A. and P. A. Rosenberg, New England Journal of Medicine, 330 (9):613-622, 1994). A large number of NMDA receptor antagonists have been synthesized and tested for interaction with the NMDA receptor complex, and research into the synthesis and improvement of NMDA receptor antagonists is continuing. See, for example, U.S. Pat. No. 5,783,700, WO 97/10240, U.S. Pat. No. 5,710,168, WO 98/03189, and DE 19601782.

For example, the NMDA receptor antagonist memantine has a three-ring structure with a bridgehead amine group which is charged at physiological pH and two methyl side groups that stabilize its interaction with the NMDA receptor (Lipton S A, Trends Neurosci 16:527-532, 1993; Chen H-S V and Lipton S A, J Physiol. (Lond) 499:27-46, 1997; Chen H S et al., J Neurosci. 12:4427-4436, 1992 and Chen H-S V et al., Soc Neurosci Abstr. 24:342, 1998) (see also FIG. 6). Memantine is a voltage dependent, moderate-affinity, non-competitive NMDA-receptor antagonist that acts primarily during pathological conditions (e.g., excessive NMDA receptor activation) without affecting normal synaptic activity and physiological functions (Chen H-S V and Lipton S A, J Physiol. (Lond) 499:27-46, 1997 and Chen H S et al., J Neurosci. 12:4427-4436, 1992). Both memantine (e.g., 1-amino-3,5-dimethyladaman-tane hydrochloride) and modified memantine molecules (e.g., memantine derivatives having increased specificity and/or bioavailability, decreased side effects or metabolic rate or additional mechanism(s) of action at the NMDA receptor) are envisioned for use in the invention.

NMDA receptor antagonists also include newer preparations under development e.g., CP 101, 606 (Di, X. et al., Stroke. 28:2244-2251, 1997) BIII CL (Grauert, M. et al., J. Pharmacol. Exp. Ther., 285:767-776, 1998); AR-R15896AR (Palmer, C. G. et al., J. Pharmacol. Exp. Ther., 288:121-132, 1999) LY274614 (Tiseo, P. J. and Inturrisi C. E., J. Pharmacol. Exp. Ther., 264:1090-1096, 1993); and NMDA antagonists that act on the glycine B site (Danysz, W. and C. G. Parsons, Pharmacol. Rev., 50:597-664, 1998).

Many different types of assays, with many variations of each type, have been used by those of skill in the art to test compounds for the properties of an NMDA receptor antagonist. Triton-treated membrane fractions prepared from rat telencephalon (including cortex, hippocampus, and striatum) can be used in binding assays to determine K_D'S of compounds; the effects of various compounds on [³H]glycine binding can be determined, yielding a K_i, (Kessler, M. et al., J. Neurochem, 52:1319-1328, 1989). Ebert, B. et al. (Eur. J. Pharmacol. Mol. Pharmacol., 208:49-52, 1991) have described assays that determine K_i values of compounds by evaluating their affinities to membrane fractions isolated from various parts of the rat brain. It was found that the test compounds showed markedly lower affinity for the MK-801 binding sites in the rat cerebellum compared to MK-801 binding sites in the cortex (approximately 25-fold lower). K_D values were similar for rat cortex, hippocampus, striatum, midbrain and medulla pons, although B_max values (indicating density of binding sites) for these tissues varied considerably.

In other types of tests of compounds for properties of NMDA receptor antagonists, onset and relief of block of NMDA-induced voltage-clamped neuron currents can be measured after application of a compound (Mealing, G. A. R. et al., J. Pharmacol. Exp. Ther., 288:204-210 (1999); Mealing, G. A. R. et al., J. Pharmacol. Exp. Ther., 281:376-383 (1997)). Trapping of block by NMDA antagonists has been studied by a method described also in Mealing, G. A. R. et al., J. Pharmacol. Exp. Ther., 288:204-210 (1999) and in Blanpied, T. A. et al., J. Neurophysiol., 77:309-323 (1997), measuring current amplitudes on rat cortical neurons. Tests of the effectiveness of NMDA receptor antagonists as antinociceptive agents are the rat tail-flick test and the formalin test, both described in Shimoyama, N. et al., J. Pharmacol. Exp. Ther., 283:648-652 (1997). Other assays for NMDA receptor binding and effects of this binding are referred to in the review by Danysz and Parsons, Pharmacological Reviews, 50(4):597-664, 1998.

Preferred NMDA receptor antagonists are those which have a K_D in an NMDA receptor binding assay greater than 10 μM and less than or equal to 100 μM, more preferred are those NMDA receptor antagonists which have a K_D greater than 1 μM and less than or equal to 10 μM, even more preferred are those NMDA receptor antagonists which have a K_D greater than 100 nM and less than or equal to 1 μM, still more preferred are those NMDA receptor antagonists which have a K_D greater than 10 nM and less than or equal to 100 nM, and most preferred are those NMDA receptor antagonists which have a K_D equal to or less than 10 nM.

There is evidence for three major categories of opioid receptors in the central nervous system. These have been designated μ, κ, and δ. Binding to the opioid receptors can be measured in assays such as those described in Kristensen, K. et al., Life Sciences, 55(2):PL45-PL50 (1994), using bovine caudate nucleus. Opioid receptor binders (which act either as an agonist or antagonist) are those compounds that bind to opioid receptors with a dissociation constant of less than about 100 nM. Preferably, opioid receptor binding molecules bind to opioid receptors with a K_D of less than 10 nM. A given opioid drug may interact to a variable degree with all three types of receptors and act as an agonist, partial agonist, or antagonist, at each type of receptor. The antagonist naloxone binds with high but variable affinity to all of these receptors. The term “naloxone-sensitive” is sometimes used synonymously with “opioid” in describing the actions of a given compound. See Jaffe, J. H. and W. R. Martin, “Opioid Analgesics and Antagonists,” pp. 485-521 In The Pharmacological Basis of Therapeutics, (A. G. Gilman et al., eds.), 8th ed., Pergamon Press, New York, 1990.

Compounds classified as opioids have the ability to bind to opioid receptors. These can be natural or synthetic compounds. It has been found that some opioids tested for binding to the NMDA receptor are NMDA receptor antagonists (Ebert, B. et al, Biochemical Pharamacology. 56:553-559, 1998). Within the class of compounds that are opioids and are NMDA receptor antagonists is a subset of compounds that can exist as (−) and (+) forms. Where the enantiomers have been tested for binding affinity to NMDA receptors, both have been found to have binding activity; for some of these compounds, the (+) enantiomer has been demonstrated as having a higher affinity for NMDA receptors (Gorman, A. L., et al., Neurosci. Lett., 223:5-8, 1997; Choi, D. W. and V. Viseskul, Eur. J. Pharmacol., 155:27-35, 1988; Craviso, G. L. and Musacchio, J. M., Molec. Pharmacol. Exp. Ther., 264:1090-1096, 1993).

While Applicants do not wish to be bound by a single mechanism of action of the methods of the claims, one hypothesis that explains the results observed in the Examples is that both narcotic agonists and narcotic antagonists can bind to NMDA receptors and act as antagonists of NMDA receptors. Support for this hypothesis can be found in the scientific literature: (1) narcotic agonists and antagonists bind to NMDA receptors (see study of inhibition of binding of [³H]dextromethorphan in Craviso, G. L. and J. M. Musacchio, Molec. Pharmacol., 23:629-640, 1983); (2) both (+) and (−) enantiomers can bind to NMDA receptors, with the (+) enantiomer in most cases having a higher affinity for the NMDA receptor (see Craviso, G. L. and Musacchio, J. M. Molec. Pharmacol., 23:629-640, 1983); also see study of inhibition of binding of MK-801 to NMDA receptors in synaptic membranes from rat forebrain in Gorman, A. L. et al., Neurosci. Lett., 223:5-8, 1997); (3) like compounds previously characterized as NMDA antagonists, narcotic agonists and antagonists can protect cultured neurons from glutamate toxicity (Choi, D. W. and Viseskul, V. Eur. J. Pharmacol., 155:27-35, 1988).

Assuming that both (+) and (−) enantiomer of narcotic antagonists decrease stereotypic behaviors by blocking NMDA receptors, there are considerable advantages to be gained by employing (+) enantiomers. These are: (1) there is no induction of narcotic receptors; (2) narcotics can be employed for pain relief if necessary (e.g. oral surgery or other surgery), as (+) enantiomers of narcotic antagonists do not block narcotic analgesia. The (+) enantiomers, unlike some known NMDA antagonists, readily cross the blood brain barrier. They do not produce toxic side effects like dizocilpine (MK-801). There is much experience with dextromethrophan as an anti-tussive with very little toxicity. Furthermore, there is considerable experience in treating addiction with (−) naltrexone and with racemic methadone. Toxicity of these substances is minimal.

Substituting (+) methadone for racemic methadone or (−) acetyl-1 methadol in the treatment of narcotic addicts would have many advantages, including: 1) decreased craving without maintaining addiction; 2) no tolerance, and therefore lower doses; 3) no problems with security or drug diversion; and 4) less difficulty in weaning addicts. Block of NMDA receptors should also decrease craving for cocaine and alcohol (Sass, H. et al., Arch. Gen. Psychiarty, 53:673-680, 1996; Mitchem, L. D. et al., Pharmacol. Biochem. Behavior, 62:97-102, 1999).

Preferred compounds to be used in the treatment of repetitive behavior disorders include (+) enantiomers of both natural and synthetic opioids, such as dextromethorphan, dextrorphan, (+) methadone and (+) pentazocine; (+) enantiomers of synthetic narcotic antagonists such as (+) naloxone, (+) naltrexone, (+) nalmefene, and (+) diprenorphine.

Compositions to be used in methods described herein for the treatment of stereotypic, self-injurious and compulsive behaviors in animals and in humans include those comprising NMDA receptor antagonists; those compositions comprising NMDA receptor antagonists, wherein the composition does not comprise haloperidol; those compositions comprising NMDA receptor antagonists, wherein the composition does not comprise haloperidol, and wherein the composition does not comprise primarily (−) enantiomer of an opioid receptor agonist or antagonist; compositions comprising NMDA receptor antagonists, wherein the composition does not comprise haloperidol, and wherein the composition does not comprise an opioid receptor agonist or antagonist as the (−) enantiomer; also, compositions comprising a compound selected from the group consisting of dextromethorphan, dextrorphan, naltrexone, naloxone, methadone, pentazocine, nalmefene, diprenorphine, nalorphine, hydromorphone, oxymorphone, hydrocodone, oxycodone, buprenorphine, butorphanol, nalbuphine, fentanyl, metazocine, cyclazocine, etazocine, and a combination of any of the preceding, wherein the compounds are predominantly (+) enantiomer.

Further compounds which can be used, preferably topically, in a composition for the treatment of behaviors such as psychogenic excoriation and scratching associated with pruritus are compounds such as loperamide, MK-801, and ketamine, wherein the compound is primarily (+) enantiomer, of those that are optically active.

Animals to be treated for repetitive behaviors include, but are not limited to, birds and mammals, for example, captive “wild” birds and mammals, such as those living in zoos or animal preserves, especially species that are predatory or can be predatory, such as feline, canine and ursine species, domestic animals, such as those raised for meat or furs (e.g., chickens, pigs, cattle, minks), and those animals kept as pets or for recreational purposes, such as rats, mice, cats, dogs, horses, and various types of birds, such as parrots, cockatoos, parakeets, pigeons and the like.

“Horses” as used herein includes those domesticated animals that are usually called “horses,” but also those animals that are sometimes classified by size as being ponies or miniature horses.

“Of an equine species” refers herein not only to horses, donkeys, and the like but also to equine hybrids, such as mules and hinnies.

Similarly, “of a canine species” refers herein not only to domestic dogs, but also to wild dogs and canine hybrids.

Stereotypic movement disorder of humans is characterized by “repetitive, seemingly driven, and nonfunctional motor behavior (e.g., hand shaking or weaving, body rocking, head banging, mouthing of objects, self-biting, picking at skin or bodily orifices, hitting own body).” The severity of the behavior is such that it interferes with normal activities or results in bodily injury if preventive measures were not used. Self-injurious behaviors occur in certain medical conditions associated with mental retardation (e.g., fragile X syndrome, de Lange syndrome, and Lesch-Nyhan syndrome, characterized by self-biting). See pages 118-121 In Diagnostic and Statistical Manual of Mental Disorders (DSM-IV™), American Psychiatric Association, 1994.

Smoking compulsion in humans is the urge to perform the act of smoking (tobacco cigarettes, cigars, or tobacco contained in another vessel or vehicle). The act of smoking is the physical manipulation of the cigarette or other tobacco vehicle and the conscious control of breathing that is normally performed in the course of taking in and blowing out the tobacco smoke, primarily involving the hands and mouth, in a kind of ritual. Smoking compulsion usually accompanies the well-documented nicotine addiction resulting from frequent and habitual tobacco smoking, but can be thought of as a compulsion which is separate from the craving satisfied by the administration of nicotine by a route other than smoking. This compulsion to smoke may be responsible for the failure of the simple administration of decreasing doses of nicotine (by transdermal patch or by nicotine-containing chewing gum, for example) to wean smokers from their smoking habit.

Psychogenic excoriation (also sometimes referred to as neurotic excoriation or pathologic skin picking) is a human disorder characterized by excessive scratching, picking, gouging, or squeezing the skin, and occurs in approximately 2% of dermatology clinic patients, mostly female (Gupta, M. A. et al., Compr. Psychiatry, 27:381-386, 1986). It has been hypothesized that psychogenic excoriation is an impulse control disorder which is related to obsessive-compulsive disorder, or which is a manifestation of obsessive-compulsive disorder (McElroy, S. L. et al., J. Clin. Psychiatry, 55:33-53, 1994). Patients with psychogenic excoriation have responded to serotonin reuptake inhibitors such as fluoxetine and sertraline (Gupta, M. A. and A. K. Gupta, Cutis, 51:386-387, 1993; Stein, D. J. et al., Psychosomatics, 34:177-181, 1993; Phillips, K. A. and S. L. Taub, Psychopharmacol. Bull., 31:279-288, 1993; Kalivas, J. et al., Arch. Dermatol., 132:589-590, 1996). In a study of fluvoxamine (a selective serotonin reuptake inhibitor used in the treatment of OCD) for the treatment of psychogenic excoriation, patients showed significant improvement (Arnold, L. M. et al., Journal of Clinical Psychopharmacology, 19:15-18, 1999).

In what can also be considered a related self-injurious behavior, scratching associated with pruritis has been shown to respond to peripherally acting opiates, such as loperamide (U.S. Pat. No. 5,849,761; U.S. Pat. No. 5,849,762). An animal model, using injections of a chemical irritant, can be used to test the effectiveness of agents to treat scratching associated with pruritis (Kuraishi, Y. et al., European Journal of Pharmacology, 275: 229-233, 1995).

An effective amount of an agent, a compound or a drug is an amount that produces a measurable improvement in the condition to be treated (e.g., a reduction in the frequency of the behavior exhibited in the human or animal, compared to the frequency of behaviors exhibited in a human or animal left untreated or sham-treated).

A compound primarily in the (+) form can be from greater than 50% to 100% (+) enantiomer. Similarly, a compound that is primarily (−) can be from greater than 50% (in a racemic mixture) to 100% (−) enantiomer. Compositions comprising primarily the (+) form of an opioid can have greater than 50% to 60% (+) enantiomer, but preferably have greater than 60% to 70% (+) enantiomer, more preferably greater than 70% to 80% (+) enantiomer, still more preferably greater than 80% to 90% (+) enantiomer, and most preferably, more than 90% (+) enantiomer.

Agents to be used in methods of treating a human or an animal for a repetitive and/or compulsive behavior disorder can be employed in combination with a non-sterile or sterile carrier or carriers for use with cells, tissues or organisms, such as a pharmaceutical carrier suitable for administration to a human or animal subject. Such compositions comprise, for instance, a media additive or a therapeutically effective amount of an agent and a pharmaceutically acceptable carrier or excipient. Such carriers may include, but are not limited to, saline, buffered saline, dextrose, water, ethanol, surfactants, such as glycerol, excipients such as lactose and combinations thereof. The formulation can be chosen by one of ordinary skill in the art to suit the mode of administration. The chosen route of administration will be influenced by such factors as the solubility, stability and half-life of the agent, for instance.

Agents to be used in the treatment of a repetitive and/or compulsive behavior disorder may be employed alone or in conjunction with other compounds, such as other therapeutic compounds. The pharmaceutical compositions may be administered in any effective, convenient manner, including administration by topical, oral, anal, vaginal, intravenous, intraperitoneal, intramuscular, subcutaneous, intranasal, transdermal or intradermal routes, among others. In therapy or as a prophylactic, the active agent may be administered to a subject as an injectable composition, for example as a sterile aqueous dispersion, preferably isotonic, or “packaged” as liposomes or microspheres.

When injectable compositions are desired, the functional antagonists of the present invention may be formulated, for example, into preparations for injection by dissolving, suspending or emulsifying them in an aqueous or non-aqueous solvent, such as vegetable oil, synthetic aliphatic acid glycerides, esters of higher aliphatic acids or propylene glycol; and if desired, with conventional additives such as solubilizers, isotonic agents, suspending agents, emulsifying agents, stabilizers and preservatives.

Alternatively, if one wishes to prepare an oral dosage form containing one of the functional antagonists herein encompassed, commonly used and pharmaceutically acceptable tableting excipients, such as lactose, microcrystalline cellulose, corn starch, stearic acid, or the like, may be used, if desired, to prepare such dosage forms.

Alternatively, the composition may be formulated for topical application, for example, in the form of ointments, creams, lotions, eye ointments, eye drops, ear drops, mouthwash, impregnated dressings and sutures and aerosols, and may contain appropriate conventional additives, including, for example, preservatives, solvents to assist drug penetration, and emollients in ointments and creams. Such topical formulations may also contain compatible conventional carriers, for example cream or ointment bases, and ethanol or oleyl alcohol for lotions.

In addition, the amount of the compound will vary depending on the size, age, body weight, general health, sex, and diet of the host, and the time of administration, the biological half-life of the compound, and the particular characteristics and symptoms of the disorder to be treated. Adjustment and manipulation of established dose ranges are well within the ability of those of skill in the art, and preferably minimize side effects and toxicity.

EXEMPLIFICATION

Example 1

Treatment of Cribbing in Horses

Horses were admitted to the Large Animal Hospital of Tufts University School of Veterinary Medicine or were tested in their home barn. Cribbing straps and food were removed prior to testing. Control rates of crib-biting were observed and recorded for 5 minute intervals for one hour or more after an intravenous injection of 0.15 M saline. Test drugs were administered orally (by gavage) or by injection into the jugular vein. Solutions were made up with physiological saline and sterilized by filtration through a 0.2 micron filter (Millipore).

For the experimental data shown in FIG. 1, after establishment of a stable control rate of approximately 10 crib-bites per minute, 50 mg of (+)-methadone-HCl in 25 ml saline was injected i.v. In FIG. 1, the cumulative number of crib-bites was plotted against time as was the rate per 5 minute interval (Shuster, L. and N. H. Dodman, pp. 185-202, In Psychopharmacology of Animal Behavior Disorders, (N. H. Dodman and L. Shuster, eds.), Blackwell Scientific, Malden, Mass., 1998). The rate decreased between the second and the fifth 5-minute interval following injection. The control rate then resumed during the next 80 minutes of observation. Horses were observed continuously during scoring for side effects that might be attributed to the treatment. These included changes in posture, disposition and motor activity. See also Table 1.

Example 2

Treatment of Stall-Walking in Horses

Dextromethorphan-HBr, 1.0 mg/kg i.v., was injected after 60 minutes of control observations, to test its effect on a stall-walking horse. When measuring “stall walking” locomotor activity, each circuit around the stall was scored as one rotation. Cumulative rotations per 5 minute interval were plotted against time to establish the rate of circling. The results of the experiment are plotted in FIG. 2. See also Table 1.

TABLE 1
Effect of some Drug Treatments on the Rate of Crib Biting
			Crib-biting
			Frequency	Number
			number per	per
			minute	minute
		Duration	Before	After
Horse	Drug Dose & Route	of Effect	treatment	treatment
CB	(−) naloxone	65 min.	12	0.1
	.04 mg/kg, i.v.	(10 min lag)
CB	(+) naloxone	60 min.	10	6.6
	0.12 mg/kg, i.v.	(30 min lag)
CB	(+) naloxone	60 min.	9.2	0.8
	0.18 mg/kg, i.v.	(no lag)
CB	Dextromethorphan	90 min.	8	1.7
	1.0 mg/kg, p.o.	(35 min lag)
CB	Dextromethorphan	35 min	7.6	0.3
	1.0 mg/kg, i.v.	(no lag)
CB	(+) Methadone	20 min	8.8	2.6
	0.2 mg/kg, i.v.	(10 min lag)
CB	(+) Methadone	10 min	8.2	5.5
	.01 mg/kg, i.v.
CB	ketamine	50 min	8.2	1.3
	0.2 mg/kg, i.v.	(no lag)
Frito	Dextromethorphan	100 min	3.5	1.8
	3.2 mg/kg p.o.	(30 min lag)
Full	Dextromethorphan	45 min	3.5 turns	.3 turns
Circle	1.0 mg/kg,. i.v.	(no lag)	per min.	per min.
(turning)

Example 3

Treatment of Light/Shadow-Chasing in Dogs

Behavior of a shadow-chasing dog was filmed with a video camera for 10 minutes after the onset of testing in the owner's home. To stimulate the dog, the owner moved around a flashlight beam on the floor for 5 seconds. The typical response after the light was turned off was frantic searching for the light followed by fixed staring at the floor. Dextromethorphan-HBr, 2 mg per kg p.o. was administered twice daily and testing was carried out one hour after the morning dose. Results are shown in FIG. 3.

Example 4

Mouse Model for Pruritus

The animals used were BALB/c male mice, weighing 27-33 g. One mouse was used per compound tested, except for two control mice receiving saline; two different mice were tested with (+) methadone, each with a different dose. Compound 48-80 (Kuraishi, Y. et al., European Journal of Pharmacology, 275:229-233, 1995), 0.5 mg/ml in saline, was injected subcutaneously in a volume of 0.1 ml, between the shoulder blades of the mouse. Test compounds, dissolved in saline, were injected intraperitoneally in a volume of 0.1 ml per 10 g, either 10 minutes before or 30 minutes after injection of compound 48-80. The cumulative number of scratches with a hind leg were recorded at 10 minute intervals for 60 minutes following the injection of compound 48-80. See Tables 2 and 3, as well as FIGS. 4, 5A and 5B, showing the effectiveness of the compounds tested: naltrexone, dextromethorphan, (+) methadone, haloperidol, and (+) naloxone.

TABLE 2
Effect of NMDA Blockers on Pruritus in Mouse: Blocker Administered 10
Minutes Before 48-80
	Cumulative Scratches
	Time		Naltrexone	Dextromethorphan
	Minutes	Control	10 mg/kg	10 mg/kg
	10	5	0	1
	20	52	0	57
	30	166	0	105
	40	277	1	157
	50	364	61	182
	60	498	73	192
Time	(+) methadone 10 mg/kg	Control
10	0	3
20	0	79
30	0	99
40	0	227
50	0	404
60	0	456

TABLE 3
Effect of NMDA Blockers on Pruritus in Mouse: Compound administered 30
minutes after 48/80
	Cumulative Scratches
		(+)	(+)	(+)
		Methadone	Methadone	Naloxone	Dextromethorphan	Haloperidol
Time	Saline	5 mg/kg	10 mg/kg	20 mg/kg	20 mg/kg	2.0 mg/kg
10	4	0	6	4	47	2
20	70	56	38	48	125	87
30	134	114	106	105	158	108
40	181	145	107	112	171	137
50	220	210	107	146	178	137
60	297	267	107	175	185	142

Example 5

Treatment of Compulsive Scratching in Mice Using Memantine

Compulsive scratching was produced by injecting mice subcutaneously with either serotonin or compound 48-80 which degranulates mast cells to release serotonin. The cumulative number of scratches with a hind leg was recorded at 5 minute intervals for the next 30 minutes. Treated animals were injected intraperitoneally 5 minutes prior to inducer with memantine, while controls received saline intraperitoneally. Mean values were calculated, and the significance of differences between the treated and control groups determined with Student's t test or by the non-parametric Mann-Whitney U Test (p<0.05). At 2 mg/kg and 5 mg/kg, memantine decreased scratching induced by both 48-80 compound (FIG. 7) and serotonin (FIG. 8). However, p-values did not achieve significance because of small sample size and considerable individual variability among controls (see Table 4).

TABLE 4
Effect of Low Dosages of Memantine on Compulsive Scratching Induced in Mouse
by Serotonin and 48-80
	Drug %	p value
		#Treatment	Mean		of		Mann
n	Pre-treatment	(SC)	Scratches	SE	Control	t Test	Whitney
5	Saline	Serotonin	492	152
5	Memantine 2 mg/kg	Serotonin	200	119	41%	0.071	0.076
5	Saline	Serotonin	337	127
5	Memantine 5 mg/kg	Serotonin	210	101	62%	0.594	0.465
5	Saline	48-80	248	50
5	Memantine 5 mg/kg	48-80	135	51	54%	0.182	0.175
10	Saline	48-80	356	97
10	Memantine 2 mg/kg	48-80	191	78	54%	0.254	0.096
# of subcutaneous (SC) injections:	0.1 mL of Serotonin at 0.4 mg/mL
	0.1 mL of 48-80 at 1.0 mg/mL

Thus, the effect of higher doses of memantine on compulsive scratching induced in mice was tested. Memantine administered at 15 mg/kg significantly inhibited compulsive scratching induced by serotonin (see Table 5 and FIG. 9). Similarly, when memantine was injected into mice at 30 mg/kg, compulsive scratching induced by serotonin was significantly reduced compared to mice injected with saline (see Table 6 and FIG. 10). The findings demonstrated that memantine was effective at treating obsessive-compulsive scratching in mice at higher doses.

TABLE 5
Effect of Memantine at 15 mg/kg on Compulsive Scratching Induced in Mouse by
Serotonin
	Weight	Pre-treatment		Time (min)
ID#	(g)	(IP)	Treatment	0	5	10	15	20	25	30
87	62.6	Memantine	5HT .4 mg/mL	0	0	0	0	7	7	7
		15 mg/kg	(0.1 mL)
68	58.4	Memantine	5HT .4 mg/mL	0	0	0	9	24	40	40
		15 mg/kg	(0.1 mL)
35	48.9	Memantine	5HT .4 mg/mL	0	0	0	0	0	0	0
		15 mg/kg	(0.1 mL)
69	59.0	Memantine	5HT .4 mg/mL	0	0	9	33	63	63	63
		15 mg/kg	(0.1 mL)
66	58.3	Memantine	5HT .4 mg/mL	0	0	0	0	0	0	0
		15 mg/kg	(0.1 mL)
88	62.4	Saline	5HT .4 mg/mL	0	35	134	210	315	328	384
			(0.1 mL)
86	68	Saline	5HT .4 mg/mL	0	94	105	289	300	362	362
			(0.1 mL)
34	50.5	Saline	5HT .4 mg/mL	0	32	191	307	333	333	333
			(0.1 mL)
70	54.6	Saline	5HT .4 mg/mL	0	0	88	109	260	354	371
			(0.1 mL)
67	69.2	Saline	5HT .4 mg/mL	0	0	0	79	105	186	212
			(0.1 mL)
	Time (min)
	0	5	10	15	20	25	30
Summary
Memantine
15 mg/kg
Total	0	0	9	42	94	110	110
Mean	0	0	1.8	8.4	18.8	22	22
SD	0	0	4.024922	14.29336	26.58383	28.27543	28.27543
SE	0	0	1.8	6.392183	11.88865	12.64516	12.64516
Summary
Saline
Total	0	161	518	994	1313	1563	1662
Mean	0	32.2	103.6	198.8	262.6	312.6	332.4
SD	0	38.40833	69.89492	102.9378	92.12112	72.17202	69.8663
SE	0	17.17673	31.25796	46.0352	41.19782	32.27631	31.24516
p value	0	0.134111	0.032026	0.017442	0.004222	0.000426	0.000335

TABLE 6
Effect of Memantine at 30 mg/kg on Compulsive Scratching Induced in Mouse by
Serotonin
	Weight	Pre-treatment
ID#	(g)	(IP)	Treatment	0	5	10	15	20	25	30
1	55.1	Memantine	5HT .4 mg/mL	0	5	16	58	58	58	58
		30 mg/kg	(0.1 mL)
3	60.1	Memantine	5HT .4 mg/mL	0	0	5	12	12	20	20
		30 mg/kg	(0.1 mL)
27	53.7	Memantine	5HT .4 mg/mL	0	35	54	63	63	74	85
		30 mg/kg	(0.1 mL)
29	62.7	Memantine	5HT .4 mg/mL	0	0	6	12	12	12	19
		30 mg/kg	(0.1 mL)
89	59.5	Memantine	5HT .4 mg/mL	0	11	15	43	62	90	96
		30 mg/kg	(0.1 mL)
2	47.7	Saline	5HT .4 mg/mL	0	228	402	584	649	736	853
			(0.1 mL)
26	57.6	Saline	5HT .4 mg/mL	0	22	127	303	359	359	476
			(0.1 mL)
28	48.2	Saline	5HT .4 mg/mL	0	71	120	312	391	486	657
			(0.1 mL)
30	58.2	Saline	5HT .4 mg/mL	0	15	39	69	117	247	458
			(0.1 mL)
90	38	Saline	5HT .4 mg/mL	0	35	155	310	459	527	548
			(0.1 mL)
	0	5	10	15	20	25	30
Summary
Memantine
30 mg/kg
Total	0	51	96	188	207	254	278
Mean	0	10.2	19.2	37.6	41.4	50.8	55.6
SD	0	14.58424	20.09229	24.50102	26.90353	33.8408	35.73933
SE	0	6.52227	8.985544	10.95719	12.03162	15.13407	15.98312
Summary
Saline
Total	0	371	843	1578	1975	2355	2992
Mean	0	74.2	168.6	315.6	395	471	598.4
SD	0	88.64367	137.4311	182.3823	191.8385	184.5982	162.3955
SE	0	39.64265	61.46104	81.56384	85.79277	82.55483	72.62548
p value	0	0.183922	0.074134	0.020409	0.010411	0.004605	0.001295

Example 7

Treatment of Dogs Having Compulsive Behaviors with Memantine

Between 2 and 5 percent of dogs seen by veterinary behaviorists are diagnosed with compulsive disorders. Common compulsive behaviors in dogs include tail chasing, circling, flank or blanket sucking, fly snapping or light/shadow chasing. Selective serotonin reuptake inhibitors (SSRIs) are the typical treatment for obsessive compulsive disorder/behaviors in humans and animals; however, SSRIs and clomipramine are not effective in all OCD cases. For example, only 43% to 60% of people suffering from OCD show a response when treated with SSRIs (or serotonin reuptake inhibitors (SRIs)) and the average reduction in OCD symptoms in those people who respond to treatment is generally only 23% to 43%. Thus, other treatment options are needed for both humans and other animals suffering from obsessive-compulsive disorders.

The effect of the NMDA receptor antagonist memantine on dogs of differing breeds and having various types of repetitive, self-injurious or obsessive-compulsive disorders was evaluated (see Table 7 for treatment data and dog characteristics). The response of the dogs to the treatment was evaluated by the dogs' owners based on the frequency and intensity of the compulsive behaviors (see Table 8).

TABLE 7
Characteristics of Dogs Treated with Memantine
			Age		Treated
No.	Breed	Sex	(months)	OCD	before
1	Dachshund	Female,	13	Spinning	Yes,
		spayed			treatment-
					resistant on
					fluoxetine and
					clomipramine,
					no current
					treatment
2	German	Male	6	Tail chasing,	No
	Shepherd			compulsive
				ball playing
3	Doberman	Male,	36	light/shadow	No
		cas-		chasing,
		trated		blanket
				sucking
7	Golden	Female,	48	Tail chasing,	No
	retriever	spayed		grass ripping
	cross

TABLE 8
Scoring of dogs treated for compulsive behaviors
1	2	3	4	5	6	7
75%	50%	25% better	No	25% worse	50% worse	75%
better	better		change			worse

Although dogs can be treated with memantine doses ranging from 0.1 mg/kg to mg/kg, and have been treated with doses of memantine ranging from 0.5 mg/kg to 1.5 mg/kg (N. Dodman, unpublished data), memantine at 0.3 mg/kg to 0.5 mg/kg was administered to the above-described dogs twice a day. Fifty percent of the dogs responded to memantine treatment (see FIG. 11). Responder dogs (dogs 1 and 3) saw a reasonable level of improvement in their behaviors (see FIG. 12). In these improved dogs, a response was typically seen within the first five days of treatment. Ambulatory and predatory compulsive disorders, such as light/shadow chasing and spinning improved, while only one oral compulsive behavior (e.g., blanket sucking) improved. Although sample size was small, memantine was helpful in treating some cases of canine obsessive-compulsive disorder and, in the case of dog 1, resulted in improvement of behavior that had previously been non-responsive to other drugs.

Example 8

Case Study of a Dog with Compulsive Spinning Behavior Treated with Memantine

History

A 13-month old spayed female Miniature Dachshund weighing 2.5 kg (5.5 lbs) was evaluated for daily repetitive circling behavior (“spinning”) (dog 1, Table 7). The dog resided with a single female owner who was fostering dogs for a Dachshund rescue organization. At the time the dog was acquired, eight other Dachshunds and one Cocker Spaniel lived in the household.

The dog was released by the breeder to a Dachshund rescue organization at the age of eight weeks. It reportedly had shown spinning behavior since the age of six weeks. The owner started to foster this dog when it was 4 months old. At the same time, the owner was also fostering the dog's 1-month younger half-sibling, who had the same sire. This half-sibling showed compulsive pacing in wide circles, especially at night. He was eventually euthanized at the age of 8 months because of severe injuries he sustained while pacing. The breeder acknowledged later that another puppy from the same sire also had similar “neurological” issues.

The female Dachshund was kept inside the owner's home together with the other dogs, from whom she was separated by a baby gate in the kitchen when the owner was not at home. A crate was used from time to time to reduce the risk of the dog injuring itself when it was spinning.

The whole time the owner fostered the dog, it circled in very tight circles to the left, pivoting on its hind limbs. During the dog's first estrus at 8 months, the spinning episodes improved slightly for a short while. The dog was subsequently spayed and at around that time started circling to the right from time to time. While spinning to the right, the dog was again spinning in tight circles with its front end as the pivotal point. The spinning behavior was especially marked in the evening: the owner described the behavior as being more “obsessive and intense” at that time. On bad days, the dog did not eat her evening meal but circled instead. When offered a toy, the dog sometimes stopped for a moment to grab the toy and then spun with the toy in its mouth. The dog also followed the owner around the house sometimes in the evening, running in close proximity to her feet. If the owner stood still for a moment, the dog started spinning. When spinning, the only way to interrupt the dog was to pick it up and hold it tight until it calmed down. While being held, the dog would keep struggling and moving as if trying to break free. The owner said that the dog displayed spinning behavior for about 6-10 hours each day. The only observed changes in frequency and presentation of the spinning were the slight improvement and the circling to the right at the time of the first heat and for a short while when it settled in the new home. The owner made sure to pay no attention to the spinning behavior except when the dog was in danger of injuring herself. The dog would not stop spinning even when it bumped into furniture and injured itself.

On some nights the dog did not spin but stared on an imaginary spot on the floor while yelping and crying. The owner was able to interrupt this behavior by interacting with her dog. As soon as the interaction ended, the dog engaged again in yelping and focusing on one spot.

The dog did not interact a lot with the owner or the other dogs in the household. Initially, she would not even make eye contact with the owner or respond to her name being called. This improved somewhat over time. When together with the other dogs, she sometimes ran around with them but started spinning whenever they stopped running. She rarely played with the other dogs or interacted with them for any length of time.

The owner described the dog as being excited and constantly moving around every day before bedtime. If the owner was not present, the dog was not able to fall asleep. To calm the dog down enough for her to sleep, the owner resorted to holding her tightly until she calmed down enough to fall asleep. This daily struggle could last up to 30 minutes. On rare occasions when the dog woke up at night, she felt very hot, panted heavily and had an elevated heart rate. The dog would then drink water or stand with her front feet in the water bowl for a while, apparently to cool down. One week before she was seen at a behavior clinic, the dog had another episode like that. She then fell over, paddled with all four legs, and eventually went limp for a while. The description of the episode sounded like a grand mal seizure.

The owner could not identify clear triggers for the spinning behavior and fixating on an imaginary spot other than excitement at evening time.

Physical Examination Findings/Previous Treatment

When the dog was about five months old, the owner brought her and her half-brother to see a neurologist. Together with the local veterinarian the neurologist ruled out blood glucose and electrolyte imbalances, neospora infection, liver shunt, lysosomal storage disease and lead poisoning. An MRI and CT were performed to rule out hydrocephalus or other CNS problems. No significant abnormalities were found with either imaging method. Treatment of the dog with an unknown dose of fluoxetine was tried for three weeks. Since that did not have the desired effect and made the dog lethargic, treatment with clomipramine at a dose of 2 mg/kg twice a day was started. The dog was maintained on this treatment for four weeks but showed no notable improvement. The same treatment was also tried with the half-brother, also without success. After the incident that appeared to be a grand mal seizure, the female Dachshund was treated with 2.5-5 mg of diazepam once a day at night to help her fall asleep. The neurologist stated that the dog's brain development might be abnormal and recommended seeing a veterinary behaviorist.

On presentation for the behavior consultation the dog was found to be in good physical condition. A scar on the left eye caused by an injury incurred during a spinning episode was obvious. The spinning behavior was not seen in the consulting room, but the owner provided video tapes of the behavior.

Diagnosis

Many possible medical reasons for the dog's circling behavior were ruled out by previous evaluations and procedures. Based on the consistent, repetitive nature of the spinning behavior and the fact that circling was to either side, a preliminary diagnosis of canine compulsive disorder was made. However, an idiopathic seizure disorder could not be ruled out completely.

Treatment

Since the dog was previously treatment resistant to fluoxetine and clomipramine, the dog was started on the N-methyl-D-aspartate (NMDA) receptor antagonist memantine. The starting dose was 0.4 mg/kg twice a day. Because of the low weight of the patient, memantine liquid (2 mg/ml) was used. The owner was notified that possible side effects might include ataxia, tremor, prone position or bradypnea. She was asked to immediately report back if any of these or other side effects were seen. Further treatment recommendations included daily aerobic exercise and environmental enrichment, including the use of chew toys and food puzzles. The importance of structure and consistent interactions were discussed as well as the importance of trying to identify possible triggers for the spinning behavior. The owner was asked to report back on a daily basis to assess changes in the spinning behavior. She was advised to take into account both the intensity and frequency of the compulsive behavior when assessing improvement or worsening of the spinning.

Follow-Up

On the second day of pharmacological treatment the owner reported 25% improvement. The dog showed less spinning and also engaged in playing with food and chew toys. After three days the dose of memantine was increased to 0.5 mg/kg twice a day. After this dose adjustment the owner reported more and longer social interactions between the dog and her as well as between the dog and the other dogs in the household. Furthermore, the intensity and frequency of the spinning were decreased. The owner was able to interrupt her dog more easily and rated the compulsive behavior as 50% improved compared to the time before the memantine treatment (see also FIG. 12, dog 1). She also noted that the dog appeared “happier” and was more active. After five days on that dose, the next dose adjustment was done. The memantine dose was increased to 0.8 mg/kg twice a day for one day and then to 1 mg/kg twice a day. The owner reported regression at this dose rate and felt that the behavior had regressed to its pre-treatment level. The dose was reduced to 0.6 mg/kg in the morning and 0.8 mg/kg at night. On the reduced dose the owner saw improvement again, but not back to the earlier level of 50% improved.

All references cited herein not previously specifically stated as being incorporated by reference are hereby incorporated by reference in their entirety.

While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A method for treating a repetitive behavior disorder or obsessive-compulsive disorder in an animal, comprising administering to the animal a composition comprising an effective amount of memantine.

2. The method of claim 1 wherein the animal is from a species selected from the group consisting of the primate species, the equine species, the canine species, the feline species, the ursine species, the ovine species and the bovine species.

3. The method of claim 2 wherein the animal is of the equine species and wherein the animal is a horse.

4. The method of claim 3 wherein the repetitive behavior disorder or obsessive-compulsive disorder is manifested by one or more behaviors selected from the group consisting of: crib biting, wind sucking, stall walking, weaving, head bobbing, pawing, tonguing, self-biting, flank sucking and head shaking.

5. The method of claim 2 wherein the animal is of the canine species and wherein the animal is a dog.

6. The method of claim 5 wherein the repetitive behavior disorder or obsessive-compulsive disorder is manifested by one or more behaviors selected from the group consisting of: compulsive licking, acral lick, tail chasing and whirling, spinning, pacing, fly chasing, shadow or light chasing, excessive barking, stone eating, excessive drinking and excessive eating.

7. The method of claim 2 wherein the animal is of the primate species and wherein the animal is a human.

8. The method of claim 7 wherein the repetitive behavior disorder or obsessive-compulsive disorder is manifested by one or more behaviors selected from the group consisting of checking, counting, cleaning and washing to remove contamination, trichotillomania, psychogenic excoriation, scratching associated with pruritis, nail biting, hoarding, doing projects repeatedly, excessively performing rituals involving tapping or touching objects, counting, praying, list-making, blinking, staring, compulsive exercising, compulsive overeating, compulsive gambling, smoking compulsion, drug addiction and alcohol addiction.

9. A method for treating a repetitive behavior disorder or obsessive-compulsive disorder in a human comprising administering to the human a composition comprising an effective amount of memantine.

10. The method of claim 9 wherein the composition comprises about 5 mg to about 40 mg of memantine.

11. The method of claim 10 wherein the composition is administered at least once per day.

12. A method for treating a repetitive behavior disorder or obsessive-compulsive disorder in a dog comprising administering to the dog a composition comprising an effective amount of memantine.

13. The method of claim 12 wherein the composition is administered at a concentration of about 0.1 milligrams/kilogram (mg/kg) to about 10 mg/kg.

14. The method of claim 13 wherein the composition is administered at least once per day.

15. A method for treating a repetitive behavior disorder or obsessive-compulsive disorder in an animal of an equine species comprising administering to the animal a composition comprising an effective amount of memantine.

16. The method of claim 15 wherein the repetitive behavior disorder is selected from the group consisting of crib-biting and stall-walking.

17. The method of claim 16 wherein the composition is administered at a concentration of about 0.1 mg/kg to about 5 mg/kg.

18. The method of claim 17 wherein the composition is administered at least once per day.