Process for production of crystals of a medicinally effective ingredient, crystals obtained thereby and pharmaceutical preparations containing them

Abstract

The process for making crystals of a medicinally effective ingredient having a predetermined average particle size in a predetermined size range and a maximum particle size that does not exceed a predetermined maximum value, includes subjecting a supersaturated solution containing the medicinally effective ingredient to a wet milling by a wet milling apparatus while crystallizing, in order to obtain a primary particle suspension. Crystals obtained according to this process and pharmaceutical preparations containing them are also described.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to a process for production of crystals a medicinally effective ingredient, whose average particle size is in a predetermined range and whose maximum particle size does not exceed a predetermined value, to the crystals obtained thereby and to the pharmaceutical preparations containing them, especially to low-dosage preparations.

[0003] 2. Description of the Related Art

[0004] Most a medicinally effective ingredients are crystallized from a suitable solvent. A large-particle-sized crystallizate is produced in a conventional cooling or displacement crystallization. The final particle size distribution, which is suitable for certain pharmaceutical preparations and dosages, is produced after isolation and drying of crystallates of this type.

[0005] The crystallizate is micronized in a jet mill to obtain the required uniformity of effective-ingredient distribution (CUT) and dissolution kinetics, especially for low-dosage preparations. Average grain sizes of from 1.5 to 5 μm are obtained. An enormous increase in surface area as well as a thermodynamic activation of the surface occurs by partial amorphization and/or by considerable destruction or perturbation of lattice structure. A series of disadvantages are connected with this process, which are described in the literature (Thibert and Tawashhi: “Micronization of Pharmaceutical Solids”, MML Series, Volume 1, Ch. 11, pp. 328-347; Otsuka, et al, “Effect of Grinding on the Crystallinity and Chemical Stability in the Solid State of Cephalothin Sodium”, Ind. J. Pharmaceutics 62, pp. 65-73 (1990)). The effective ingredient can be strongly destablized by the partial amorphization. Chemical decomposition increases during interaction with the adjuvant substances in the pharmaceutical composition. An unstable physical structure is produced by recrystallization of the amorphous components. This leads to impairment of the dissolution properties and changes in the particle sizes during deposition of the effective ingredient, and also in the production equipment. Agglomeration and incrustation occur during micronization, which leads to an undesirable particle size distribution in the micronizate. The particle size can be influenced only to a very limited degree during micronization. Lowering the milling pressure of course leads to a slight increase in the average particle size, but also to an undesirable increase in its spread. However a certain minimum pressure is absolutely required for operation of the mill.

[0006] Micronization as a process is only suitable to a limited extent for manufacture of a physically and chemically stable medicinally effective ingredient with a particle size adjusted to fit a certain dosage range. This is also true for alternative manufacturing methods, such as manufacture of micro-fine effective ingredients from supercritical gases (Steckel, et al, “Micronizing of Steroids for Pulmonary Delivery by Supercritical Carbon Dioxide”, Int. Journal of Pharmaceutics 152, pp. 99-110 (1997)). These methods are technologically demanding and very expensive because of the high pressures employed. Spray-drying (Wendel, et al, “An Overview of Spray-Drying Applications”, Pharmaceutical Technology, October 1997, pp.124-156) is similarly suitable for production of micro-fine particles, however there is a danger of producing unstable amorphous or partially crystalline structures.

[0007] It is known from the literature that fine-grained crystals can be produced by precipitation from highly supersaturated solutions or with high stirring speeds. (B. Yu. Shekunov, et al, “Crystallization Process in Pharmaceutical Technology and Drug Delivery Design”, Journal of Crystal Growth 211, pp. 122-136 (2000); Halasz-Peterfi, et al, “Formation of Microparticles of Pharmaceuticals by Homogeneous Nucleation”, Industrial Crystallization, 1999, pp. 1-11; Affonso, et al, “Microcrystallization Methods of Aspirin”, Journal of Pharmaceutical Sciences, October 1971, pp.1572-1574).

[0008] A suitable method for producing microcrystals by rapidly cooling and intensive mixing is described in U.S. Pat. No. 3,226,389. However these crystallizates often have a large scatter and particle size agglomerates are obtained. Also the desired production of a certain particle size distribution is only possible with difficulty because of the complex interplay of super-saturation, primary and second nuclei formation and crystal growth and/or agglomerate formation.

[0009] An additional possibility for producing a definite grain size spectrum of micro-fine steroid crystals, which depends on a mechanical procedure, is described in WO A 92/08730. A crystallizate is produced from a ternary mixture, which comprises a hydrophilic solvent, a lipophilic solvent and a surfactant, by cooling in this procedure. It is indeed finer than the starting material, however the low-dose preparation is still too coarse for many applications and the same disadvantages are present, which accompany crystallizates made from highly supersaturated solutions. Contamination of the drug substance with surfactant also occurs.

[0010] In EP 0 522 700 the possibility, which is part of the state of the crystallization arts, for providing seed crystals for crystal growth by further defined cooling and heating of a partial flow, which is fed back into the crystallization process is described. With this procedure a grain size increase is obtained in the first place to a grain size largely above 100 μm, in order to improve the filtration and growth processes to obtain a high purity.

[0011] The influence of particle size and form on the CUT-value for spherical particles in solid drugs is described in M. C. R. Johnson, “Particle Size Distribution of Active Ingredient for Solid Dosage Forms of Low Dosage”, Pharmaceutica Acta Helvetiae, 47, pp. 546-559 (1972) and considering other forms in P. Guitard, et al, “Maximum Particle Size Distribution of Effective Ingredients for Solid Drugs in low dosage”, Pharm. Ind. 36, Nr. 4 (1974). The maximum particle dimensions related to the respective dosages can be calculated from the relationships described therein.

[0012] The dissolution kinetics is another important parameter for evaluating or rating the microcrystals.

[0013] The pharmaceutical performance must be continuously tested by suitable standard tests. The same goes for stability of the microcrystals as medicinally active ingredients and in pharmaceutical preparations.

[0014] The isolation and drying procedures in all the described processes for producing microcrystals in suspensions for low dose preparations can be criticized. It is very difficult to dry fine-grained moist crystallizates, without impairing the grain size distribution.

SUMMARY OF THE INVENTION

[0015] It is an object of the present invention to provide a process for making crystals of medicinally effective ingredients or ethical drugs, which does not have the disadvantages of the known prior art processes and which fulfills the requirements of low-dosage preparations.

[0016] According to the invention this object is attained by a process for making crystals of a medicinally effective ingredient, whose average grain or particle size is in a predetermined range and whose maximum particle size does not exceed a predetermined value. This process comprises subjecting a supersaturated solution containing a medicinally effective ingredient to a wet milling by means of a wetting milling apparatus while crystallizing, in order to obtain a primary particle suspension.

[0017] The term “medicinally effective ingredient”, in the context of the present invention, means a substance or mixture of substances of any type, which are active or effective ingredients in an ethical drug or a medicine. These active or effective ingredients heal, alleviate, prevent or detect sickness, diseases, body injuries or maladies in the body. Such effective or active ingredients include, e.g., certain chemical elements or chemical compounds, such as steroids, for example, 11β-{4-[(ethylaminocarbonyl)oximinomethyl]phenyl}-17β-methoxy-17α-methoxymethyl-estra-4,9-dien-3-one (subsequently designated as J956).

[0018] With the process according to the present invention it is surprisingly possible to obtain crystals which are sufficiently stable and which are adjusted in regard to their particle size parameter and thus correct in regard to pharmaceutical requirements for homogeneity of the active ingredient distribution (CUT) and dissolution kinetics for low-dosage formulations. Furthermore the particle size distribution for a certain dosage can be made with a high accuracy and reproducibility. Furthermore the process according to the invention can be performed simply, rapidly and in a cost-effective manner. The crystals can preferably be isolated without impairing their grain size distribution and dried.

BRIEF DESCRIPTION OF THE DRAWING

[0019] The objects, features and advantages of the invention will now be illustrated in more detail with the aid of the following description of the preferred embodiments, with reference to the accompanying figures in which:

[0020] FIG. 1 is a graphical illustration of the behavior of the particle size in the crystallization process according to the invention; and

[0021] FIG. 2 is another graphical illustration of the behavior of the particle size in the crystallization process according to the invention

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The average particle size preferably amounts to from 1 μm to 25 μm, especially from 7 μm to 15 μm. The maximum particle size preferably does not exceed 100 μm, more preferably 80 μm. The “maximum particle size” means that no particle has a size that is greater than the stated value. Within these limits for the average particle size and the maximum particle size the particle size distribution is selected in a beneficial way so that the pharmaceutical specifications regarding CUT and dissolution kinetics correspond to those for low-dose formulations.

[0023] In the process according to the invention a supersaturated solution of the medicinally effective ingredient is used. The solution contains the medicinally effective ingredient as a solute, which is dissolved for that purpose in a solvent. The term “solvent” is understood to encompass mixtures of different solvents. A supersaturated solution used in the process according to the invention contains more dissolved material than it would when the solution is in thermodynamic equilibrium. Supersaturated solutions, in which crystal nuclei spontaneously form, can be used in the process according to the invention.

[0024] In a preferred embodiment of the process according to the invention the supersaturated solution contains from 1 percent by weight to 60 percent by weight, preferably 5 percent by weight to 35 percent by weight, of the medicinally effective ingredient, in relation to the supersaturated solution. The above-described advantages of the process according to the invention can be achieved in an especially beneficial manner with these supersaturated solutions.

[0025] The preparation of the supersaturated solutions can occur in the usual manner. Preferably the supersaturated solution is made by dissolving the medicinally effective ingredient in a solvent at a temperature below the boiling point and subsequently cooling to a temperature above the freezing point of the solution. If the steroid J956 is used as the medicinally effective ingredient and ethyl acetate as the solvent for the supersaturated solution in the process according to the invention, the heating can occur, for example, at about 70° C., until the steroid has dissolved in the ethyl acetate and the resulting solution appears to be clear. Cooling can take place during a period from 10 minutes to one hour, preferably 15 minutes to 30 minutes, at about 35° C. One skilled in the art can ascertain the parameters for making a supersaturated solution with another solvent than ethyl acetate and with another medicinally effective ingredient other than J956 by simple tests without more.

[0026] The crystallization is advantageously performed in a vessel, which is equipped with a stirrer. For example, the crystallization vessel can be equipped for that purpose.

[0027] In the process according to the invention wet milling is performed by a wet milling apparatus during crystallization. The crystallization can proceed from the saturated solution, when the wet milling has been started. Suitable apparatus for wet milling are dispersion tools and homogenizers, such as rotor-stator apparatuses, stirring mills, roller mills and colloid mills.

[0028] The making of crystals according to the invention occurs, as described above, by crystallization from a solvent or solvent mixture, e.g. by cooling a supersaturated ethyl acetate solution. During crystallizing wet milling by a wet milling apparatus, especially a rotor-stator apparatus or a colloid mill, is performed. The wet milling is performed either shortly after crystallization has begun or before it has begun. The apparatus for wet milling can be used immediately as an additional stirring device in the crystallization vessel or in a by-pass loop that goes around the crystallization vessel. The use of the by-pass loop is especially beneficial, since the apparatus is used at the same time as a supply unit. If a rotor-stator apparatus is used, the peripheral rotation speed can be 10 m/s to 50 m/s, preferably 20 m/s to 40 m/s. A very high secondary nuclei formation rate is produced by the additional energy input caused by the wet milling, especially by the rotor-stator apparatus. The individual crystal growth is greatly reduced because of that energy input. Also the inevitably formed agglomerates are broken up in narrow gaps. Thus a fine primary particle size is the result, whose average particle size is between 1 μm and 25 μm and whose maximum particle size is not greater than 25 μm to 80 μm. These particle parameters can already be sufficient for low dose formulations.

[0029] A very fine and narrow particle size spectrum can be obtained according to the invention by this combination of two processes by suitable selection of the apparatus and process conditions, since the typically highly fine grained fraction obtained by milling is reduced by superimposed crystallization processes. The maximum grain size can be maintained very small, since the agglomerate formation is largely avoided.

[0030] In order to be able to make crystals that meet the pharmaceutical requirements, even for larger particle sizes, with a definite particle size distribution with suitable accuracy and better reproducibility, the primary suspension is preferably subjected to an oscillatory temperature profile. For that purpose the fine primary suspension produced is heated to a temperature Tmax below the solubility limit of the primary particles in the suspension and subsequently cooled slowly to a temperature Tmin, which is above the freezing point of the suspension. On heating the fine-grained fraction of the primary particle suspension is dissolved and precipitated on the particle size fraction present during the cooling process. Because of that a definite shift in the particle size distribution to the larger range occurs. Preferably Tmax is selected so that between 10 and 95, preferably 20 to 50 and more preferably about 30, percent by weight of the primary particles dissolve during the heating. The fraction of dissolved primary particles is selected according to the predetermined grain size, which again is determined by the type of low-dosage formulation. If a higher proportion of the primary particles dissolve, larger-sized particles result.

[0031] In a preferred embodiment of the process according to the invention Tmin is selected so that the dissolved primary particles substantially re-crystallize again. If it is particularly desirable to reduce the losses of effective ingredient, nearly all of the dissolved primary particles are re-crystallized on the still remaining primary particles.

[0032] It is especially preferable when the cooling from Tmax to Tmin occurs during 1 minute to 10 hours, especially during 0.5 hours to 2 hours.

[0033] The cooling side of the temperature profile should be controlled so that the fresh nuclei formation is kept as small as possible. The size of this coarsening depends on the amount of the crystallizates dissolved in the heating cycle, which again is determined by the position of both temperatures Tmax and Tmin in relation to the solubility limit and the solid concentration of the suspension. This heating-cooling cycle can be repeated often, preferably 1 to 20 times, until the desired particle size distribution is obtained. The controlling parameters are thus Tmax, Tmin and the number of cycles. The more the desired coarsening, the less Tmax should be. Thus one can approach the desired final particle size with small steps. The development of the dissolved portion of the crystallizate in the heating periods is thus dimensioned so that the maximum particle diameter increases still only to a very small extent and the coarsening occurs in the region of the fine particles. Thus, for example, during dissolution and re-crstallization of 40 percent of the J956 precipitated from a 20 percent by weight ethyl acetate solution, the average particle diameter (×50) increases from 4.9 μm to 7.8 μm while the increase of the maximum particle size (×100) is scarcely measurable. That means that the particle size distribution is considerably narrowed during growth of the average value (×50) of the particle diameter. This effect is especially advantageous for pharmaceutical applications, especially for obtaining suitable CUT values and dissolution properties.

[0034] After passing through the oscillatory temperature profile the obtained crystal suspension can be filtered and washed with a solvent, when the active ingredient is only soluble to a small extent, e.g. less than 1 percent by weight. For example, these solvents are methyl-t.-butyl ether(MTBE), hexane, heptane, water or mixtures of two or more of these solvents. Thus in subsequent drying processes, which occur preferably by a drying gas or in vacuum directly in the filtration unit, bridge formation and agglomeration of the particles are avoided.

[0035] The drying can occur by convection or vacuum drying in a stirred or moving bed.

[0036] When a conventional filtration and drying is difficult and leads to impairment of the particle size distribution produced during the crystallization, for example in the case of very fine particle sizes, alternatively the filtered and washed filter cake is suspended with a suspending liquid. The suspending liquid should be a liquid, preferably water, in which the medicinally effective ingredient is only slightly soluble, for example less than one percent by weight. The obtained suspension can be converted into the dried solid form of the medicinally effective ingredient by spray drying.

[0037] The subject matter of the invention also includes crystals of the medicinally effective ingredient, which are obtained by the above-described process according to the invention. To perform the process in the above-described manner, the detailed description of the process here is referred to.

[0038] The subject matter of the invention also includes pharmaceutical formulations or preparations, which contain the crystals of the medicinally effective ingredient obtained according to the process of the invention. As pharmaceutically effective medicinally effective ingredient, for example hard gelatin capsules or tablets with and without coatings are used for peroral administration. The drugs or medicines made with the medicinally effective ingredient should not impair the chemical and crystalline stability of the microcrystals. This can be achieved by

[0039] including a light protective means or agent with the medicinally effective ingredient, for example a colored capsule jacket or applying a colored coating;

[0040] not including a surface-increasing adjuvant, such as a highly dispersed silicon dioxide;

[0041] using no or only water as solvent or auxiliary agent, and/or

[0042] keeping the moisture content of the medicinally effective ingredient low by a sufficient drying.

[0043] An example of a suitable capsule recipe or formula is provided in Table I.

TABLE I
SUITABLE CAPSULE RECIPE FOR COMPOSITION
CONTAINING 1 MG OF J956
	SUBSTANCE	AMOUNT
	J956, microcrystalline	1.000	mg
	Microcrystalline cellulose	102.480	mg
	Magnesium stearate	0.520	mg
	Hard gelatin capsule, size 3	1	piece
	Capsule filling mass	104.000	mg

[0044] In Table II an example of a suitable tablet recipe is provided.

TABLE II
SUITABLE TABLET RECIPE FOR COMPOSITION
CONTAINING 1 MG OF J956
CORE:
J956, microcrystalline     1.00 mg
Lactose monohydrate        33.8 mg
Cornstarch                 18.0 mg
Maltodextrin (10% water)   6.0 mg
Na carboxymethyl starch    0.6 mg
Glycerol monobehenate      0.6 mg
SHELL:
Hydroxypropylmethyl        1.125 mg
cellulose
Talcum                     0.225 mg
Titanium dioxide           0.625 mg
Iron oxide, yellow pigment 0.020 mg
Iron oxide, red pigment    0.005 mg

[0045] An essential result of the invention is that microcrystals of the medicinally effective ingredient are obtained, which are chemically considerably more stable than currently known micronizates, since first they have a reduced specific surface area and second they have crystalline surfaces that are unperturbed and highly crystalline.

[0046] Another result is that the microcrystals obtained by the process according to the invention correspond in regarding to their particle size distribution and solubility properties to the pharmaceutical requirements of drugs regarding CUT and dissolution properties.

[0047] It has been shown that the obtained release values are not inferior to those using micronized solids for comparison (Table III and Table IV) for the 1 mg capsule and 1 mg tablet examples. The release values were compared in a test medium, which comprises 0.3% SDS in water, with paddle stirring, 100 rpm.

TABLE III
J956: COMPARATIVE RELEASE VALUES IN % FOR
COMPARISON OF 1 mg CAPSULE WITH A MICRONIZED
EFFECTIVE INGREDIENT TO 1 mg CAPSULE WITH
MICROCRYSTALLINE SOLIDS
PARTICLE
DIAMETER (μm)	RELEASE in %
X50	X100	0 min	10 min	20 min	30 min	45 min
3.4	25	0	90.7	97.3	98.1	99.9
5.2	30	0	89.8	93.5	93.4	95.6
6.6	43	0	93.2	95.9	96.7	96.8
8.7	43	0	93.5	96.7	98.5	99.7
14.1	87	0	90.2	95.3	96.0	96.3
Micronizate		0	92.1	94.3	94.6	94.9

[0048]

TABLE IV
J956: CUT VALUE SPREAD FOR 1 mg CAPSULE WITH A
MICRONIZED EFFECTIVE INGREDIENT VERSUS 1 mg CAPSULE
WITH MICROCRYSTALLINE SOLIDS
	PARTICLE
	DIAMETER (μm)
	X50	X100	Confidence Interval %	RSD, %
	3.4	25	2.23	3.56
	5.2	30	1.20	2.08
	6.6	43	1.08	1.57
	8.7	43	0.93	1.38
	14.1	87	1.77	2.50
	Micronizate		1.72	2.56

[0049]

TABLE V
J956: COMPARATIVE RELEASE VALUES IN % FOR
COMPARISON OF 1 mg TABLET WITH MICRONIZED
EFFECTIVE INGREDIENT TO 1 mg TABLET WITH
MICROCRYSTALLINE SOLIDS
Test Medium: 0.3% SDS in water, paddle, 100 rpm
PARTICLE
DIAMETER (μm)	RELEASE in %
X50	X100	0 min	10 min	20 min	30 min	45 min
10.6	73	0	73.7	90.3	91.85	96.6
Micronizate		0	92.1	94.3	94.6	94.9

[0050]

TABLE VI
J956: CUT VALUE SPREAD FOR 1 mg TABLET WITH A
MICRONIZED EFFECTIVE INGREDIENT VERSUS 1 mg TABLET
WITH MICROCRYSTALLINE SOLIDS
	PARTICLE
	DIAMETER (μm)
	X50	X100	Confidence Interval %	RSD, %
	10.6	73	1.16	1.70
	Micronizate		1.72	2.56

[0051] A further important result is that the pharmaceutically required particle size distribution of the medicinally effective ingredient can be produced with higher reproducibility and accuracy with the process according to the invention. In FIGS. 1 and 2 the development of the grain size or particle size in the crystallization process is illustrated. The scatter of the particle size distribution is clearly reduced and the maximum grain size is clearly only slightly increased in spite a multiple increase in the average particle size. This assists in attaining good CUT values, also for low-dosage formulations.

[0052] Furthermore the grain size distribution produced in the suspension also is maintained in the dried solid body.

TABLE VII
PARTICLE SIZE DISTRIBUTION BEFORE AND AFTER DRYING
	X10	X50	X90	X100
	Suspension*	2.62***	10.4	24	73
	After drying on filter	2.7	10.61	24	73
	Suspension**	2.11	8.6	19	51
	After spray-drying	2.25	8.03	17	43
	*suspension of J956 in ethyl acetate with 14% by weight microcrystalline J956
	**suspension of J956 in ethanol/water (90/10) with 10% by weight microcrystalline J956
	***particle diameters in μm

[0053] The following measurement procedures were used to obtain measured experimental data.

[0054] Particle Size Distribution:

[0055] Sympatec HELOS (H0445), dry dispersion system (RODOS), pressure 2 bar

[0056] Content Uniformity Test:

[0057] Content Determination according to USP/Ph. Eur. for individual capsules after elution through HPLC with external calibration

[0058] Column: LiChrosphere 5μ RP-18 encapped, 150×3 mm

[0059] Eluent: acetonitrile/water=45/55

[0060] Flow: 1 ml/min

[0061] Detection UV (272 nm)

[0062] Active Ingredient Release:

[0063] Active ingredient release measured in 1000 mL water with 0.3% sodium dodecyl sulfate, 100 rpm

[0064] Content Determination by HPLC with external calibration

[0065] Column: LiChrosphere 5μ RP-18 encapped, 150×3 mm

[0066] Eluent: acetonitrile/water=45/55

[0067] Flow: 1 ml/min

[0068] Detection UV (272 nm)

[0069] The following examples serve to illustrate the invention, but do not limit the broad concept of the invention expressed generally above or in the claims appended below.

EXAMPLES

Example 1

[0070] In a sulfonation flask with a blade mixer and a heating/cooling bath 50 g of J956 are dissolved in 200 g of ethyl acetate at 70° C. The clear solution is cooled for 15 minutes at 35° C. A rotor-stator dispersing apparatus (Ultra Turrax, T25 basic, with S25N-25F) is operated with a rotation speed of 12000 to 16000 rpm to prepare the solution. After 2 minutes crystallization begins. The Ultra Turrax is operated for an additional 10 minutes and then is shut off.

[0071] The starting suspension obtained is heated at 50° C. and subsequently cooled within an interval of 1 hour at 20° C. This procedure is repeated still twice more.

[0072] Subsequently the suspension is filtered by means of a frit and washed with 100 ml MTBE. The filter cake is washed with 1000 ml water very thoroughly and subsequently suspended with 300 g water. The suspension is spray-dried under the following conditions in a laboratory spray-drier with two nozzles (2 mm) (QVF/Yamato):

	Drying gas entrance temperature:	170°	C.
	Drying gas exit temperature:	60°	C.
	Drying gas throughput:	23	m3/min
	Spray nozzle (d = 2 mm)	2.5	bar
	Feed:	8 to 10	ml/min

[0073] Microcrystals are obtained in a separating filter of the spray-drier with the following particle size distribution:

Particle size (μm)
X10  1.75
X50  6.04
X100 36

Example 2

[0074] In a glass reactor with an anchor agitator and a double-wall heating/cooling jacket 270 g of J956 are dissolved in 1200 ml of ethyl acetate at 75° C. The clear solution is cooled for 30 minutes at 38° C. The solution is circulated from the crystallizing vessel bottom outlet and is then fed back into the crystallizing vessel by means of an external rotor-stator dispersing apparatus (IKA laboratory Pilot 2000/4 with DR module). The rotor-stator dispersing apparatus is operated with a rotation speed of 9000 rpm. After 2 to 5 minutes crystallization begins. The rotor-stator dispersing apparatus is operated for an additional 10 minutes and then is shut off.

[0075] The primary particle suspension obtained is heated at 50° C. and subsequently cooled within an interval of 1 hour 20 minutes to 20° C. This procedure is repeated still twice more. Subsequently the filter cake is filtered by a frit and washed with 500 ml MTBE. The filter cake is dried by suction with air.

[0076] Microcrystals are obtained with the following particle size distribution:

PARTICLE SIZE (μm)
	Primary particle size	Final
	X10	3	4
	X50	9	13
	X100	61	73

Example 3

[0077] In a glass reactor with an anchor agitator and a double-wall heating/cooling jacket 270 g of J956 are dissolved in 1200 ml of ethyl acetate at 75° C. The clear solution is cooled for 30 minutes at 26° C. The solution is circulated from the crystallizing vessel bottom outlet and is then fed back into the crystallizing vessel by means of an external rotor-stator dispersing apparatus (IKA laboratory Pilot 2000/4 with DR module). The rotor-stator dispersing apparatus is operated with a rotation speed of 8900 rpm. After 30 sec at 36° C. crystallization begins. The rotor-stator dispersing apparatus is operated for an additional 10 minutes and then is shut off.

[0078] The primary particle suspension obtained is heated at 55° C. and subsequently cooled within an interval of 2 hours at 20° C.

[0079] Subsequently the filter cake is filtered with a frit and washed with 500 ml MTBE. The filter cake is dried by suction with air.

[0080] Microcrystals are obtained with the following particle size distribution:

PARTICLE SIZE (μm)
	Primary particle size	Final
	X10	1.2	1.4
	X50	3.4	5.4
	X100	30	30

Example 4

[0081] In a glass vessel 63 g of testosterone undecanoate are dissolved in 130 ml of acetone and cooled to 18° C. A rotor-stator dispersing apparatus (Ultra Turrax, T25 basic, with S25N-25F) is used to prepare this solution. It is operated with a rotation speed of 12000 to 16000 rpm. After 1 minute crystallization begins. The Ultra Turrax is operated for an additional 10 minutes and then is shut off. The primary particle suspension obtained is subsequently heated at 21° C. and subsequently cooled within an interval of 30 minutes at 5° C. The suspension is filtered and washed with hexane.

[0082] The filter cake is dried by suction with air.

[0083] Microcrystals are obtained with the following particle size distribution:

PARTICLE SIZE (μm)
	Primary particle size (μm)	1st Cycle (μm)
	X10	6	17
	X50	21	41
	X99	100	100
	X100	120	120

Example 5

[0084] In a glass vessel 13 g of gestagen are dissolved in 130 ml of ethyl acetate (2.3% vol) mixture and cooled to 35° C. A rotor-stator dispersing apparatus (Ultra Turrax, T25 basic, with S25N-25F) is used to prepare this solution. It is operated with a rotation speed of 22000 rpm. After 1 minute crystallization begins. The Ultra Turrax is operated for an additional 10 minutes and then is shut off. The primary particle suspension obtained is subsequently heated at 45° C. and subsequently cooled within an interval of 30 minutes at 15° C. The suspension is filtered and washed with hexane.

[0085] The filter cake is dried by suction with air.

[0086] Microcrystals are obtained with the following particle size distribution:

PARTICLE SIZE (μm)
	Primary particle size (μm)	End (μm)
X10	4	8
X50	15	21
X99	51	51
X100	61	61

Example 6

[0087] In a glass vessel 28 g of norethisterone acetate are dissolved in 140 ml of methanol and cooled to 29° C. A rotor-stator dispersing apparatus (Ultra Turrax, T25 basic, with S25N-25F) is used to prepare this solution. It is operated with a rotation speed of 22000 rpm. After 1 minute crystallization begins. The Ultra Turrax is operated for an additional 10 minutes and then is shut off. The primary particle suspension obtained is subsequently heated at 34° C. and subsequently cooled within an interval of 1 hour 15 minutes at 5° C. The suspension is filtered and washed with hexane.

[0088] The filter cake is dried by suction with air.

[0089] Microcrystals are obtained with the following particle size distribution:

PARTICLE SIZE (μm)
	Primary particle size (μm)	End (μm)
X10	4	8.5
X50	14	30.4
X99	55	87
X100	87	100

Example 7

[0090] In a glass vessel 50 g of methylnortestosterone are dissolved in 250 ml of ethanol and cooled to 20° C. A rotor-stator dispersing apparatus (Ultra Turrax, T25 basic, with S25N-25F) is used to prepare this solution. It is operated with a rotation speed of 22000 rpm. At the same time 375 ml of water are added. Crystallization begins immediately. The Ultra Turrax is operated for an additional 10 minutes and then is shut off. The primary particle suspension obtained is subsequently cooled at 21° C. The suspension is filtered and washed with water, suspended in water to form a 10 % suspension and spray-dried.

[0091] Microcrystals are obtained with the following particle size distribution:

PARTICLE SIZE (μm)
	Primary particle size (μm)	Spray-dried (μm)
X10	1.32	1.36
X50	3.96	3.94
X99	14	14
X100	18	18

[0092] The disclosure in German Patent Application 102 18 106.3 of Apr. 23, 2002 is incorporated here by reference. This German Patent Application describes the invention described hereinabove and claimed in the claims appended hereinbelow and provides the basis for a claim of priority for the instant invention under 35 U.S.C. 119.

[0093] While the invention has been illustrated and described as embodied in a process for production of steroid crystals, steroid crystals obtained thereby and pharmaceutical preparations containing them, it is not intended to be limited to the details shown, since various modifications and changes may be made without departing in any way from the spirit of the present invention.

[0094] Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.

[0095] What is claimed is new and is set forth in the following appended claims.

Claims

1. A process for making crystals of a medicinally effective ingredient, said crystals having an average particle size in a predetermined size range and a maximum particle size that does not exceed a predetermined maximum value, said process comprising subjecting a supersaturated solution containing said medicinally effective ingredient to a wet milling by a wet milling apparatus while crystallizing, in order to obtain a primary particle suspension.

2. The process as defined in claim 1, wherein said average particle size of said crystals of said medicinally effective ingredient is from 1 μm to 25 μm.

3. The process as defined in claim 1, wherein said predetermined maximum value is 100 μm.

4. The process as defined in claim 1, wherein said supersaturated solution contains from 1 to 60 percent by weight of said medicinally effective ingredient, based on said supersaturated solution.

5. The process as defined in claim 1, further comprising preparing said supersaturated solution by dissolving said medicinally effective ingredient in a solvent at a temperature below a boiling point of said solvent to form a resulting solution and subsequently cooling said resulting solution to a temperature above a freezing point of the resulting solution.

6. The process as defined in claim 1, wherein said crystallizing is performed in a vessel or container having a stirring device.

7. The process as defined in claim 1, wherein said wet milling apparatus is a rotor-stator apparatus, a stirring mill, a roller mill or a colloid mill.

8. The process as defined in claim 1, further comprising heating said primary particle suspension at a temperature (Tmax) below a solubility limit of primary particles of the primary particle suspension and subsequently cooling to a temperature above a freezing point (Tmin) of the primary particle suspension.

9. The process as defined in claim 8, wherein said supersaturated solution comprises a solvent and said temperature (Tmax) below said solubility limit is selected so that from 10 to 95 percent by weight of said primary particles dissolve in said solvent.

10. The process as defined in claim 9, wherein said temperature above said freezing point (Tmin) is selected so that dissolved primary particles are substantially re-crystallized.

11. The process as defined in claim 10, wherein said cooling from said temperature (Tmax) below said solubility limit to said temperature above said freezing point (Tmin) occurs during a time interval of 1 minute to 10 hours.

12. The process as defined in claim 8, wherein said heating at said temperature (Tmax) below said solubility limit and said cooling at said temperature above said freezing point are performed from 1 to 20 times.

13. Crystals of a medicinally effective ingredient, said crystals having an average particle size in a predetermined size range and a maximum particle size that does not exceed a predetermined maximum value, wherein said crystals are made by a process comprising subjecting a supersaturated solution containing said medicinally effective ingredient to a wet milling by a wet milling apparatus while crystallizing, in order to obtain a primary particle suspension.

14. The crystals as defined in claim 13, wherein said average particle size is from 1 μm to 25 μm and said predetermined maximum value is 100 μm.

15. The crystals as defined in claim 13, wherein said supersaturated solution contains from 1 to 60 percent by weight of said medicinally effective ingredient, based on said supersaturated solution, and said process comprises preparing said supersaturated solution by dissolving said medicinally effective ingredient in a solvent at a temperature below a boiling point of said solvent to form a resulting solution and subsequently cooling said resulting solution to a temperature above a freezing point of the resulting solution.

16. The crystals as defined in claim 13, wherein said supersaturated solution comprises a solvent; said process comprises heating said primary particle suspension at a temperature (Tmax) below a solubility limit of primary particles of the primary particle suspension and subsequently cooling to a temperature above a freezing point (Tmin) of the primary particle suspension and wherein said temperature (Tmax) below said solubility limit is selected so that from 10 to 95 percent by weight of said primary particles dissolve in said solvent and said temperature above said freezing point (Tmin) is selected so that dissolved primary particles are substantially re-crystallized, said cooling from said temperature (Tmax) below said solubility limit to said temperature above said freezing point (Tmin) occurs during a time interval of 1 minute to 10 hours.

17. The crystals as defined in claim 13, wherein said crystallizing is performed in a vessel or container having a stirring device and said wet milling apparatus is a rotor-stator apparatus, a stirring mill, a roller mill or a colloid mill.

18. A pharmaceutical preparation containing crystals of a medicinally effective ingredient, said crystals having an average particle size and a maximum particle size, wherein said crystals are made by a process comprising subjecting a supersaturated solution containing the medicinally effective ingredient to a wet milling by a wet milling apparatus while crystallizing, in order to obtain a primary particle suspension.

19. The pharmaceutical preparation as defined in claim 18, wherein said average particle size is from 1 μm to 25 μm and said maximum particle size is 100 μm.

20. The pharmaceutical preparation as defined in claim 18, wherein said crystallizing is performed in a vessel or container having a stirring device and said wet milling apparatus is a rotor-stator apparatus, a stirring mill, a roller mill or a colloid mill.

21. The pharmaceutical preparation as defined in claim 18, wherein said supersaturated solution contains from 1 to 60 percent by weight of said medicinally effective ingredient, based on said supersaturated solution, and said process comprises preparing said supersaturated solution by dissolving said medicinally effective ingredient in a solvent at a temperature below a boiling point of said solvent to form a resulting solution and subsequently cooling said resulting solution to a temperature above a freezing point of the resulting solution.