Compositions of iodoaniline derivatives and cellulose derivatives for visualization of the gastrointestinal tract

Abstract

Disclosed are x-ray contrast compositions for oral or retrograde examination of the gastrointestinal tract comprising an x-ray producing agent of the formula or a pharmaceutically acceptable salt thereof ##STR1## and methods for their use in diagnostic radiology of the gastrointestinal tract, whereinZ is H, halo, C.sub.1 -C.sub.20 alkyl, cycloalkyl, lower alkoxy, cyano, where the alkyl and cycloalkyl groups can be substituted with halogen or halo-lower-alkyl groups;R.sub.1 and R.sub.2 are independently H, C.sub.1 -C.sub.25 alkyl, cycloalkyl, acetyl or halo-lower-alkyl, wherein said C.sub.1 -C.sub.25 alkyl, cycloalkyl and halo lower-alkyl are optionally substituted with fluoro-lower-alkyl, aryl, lower-alkoxy, hydroxy, carboxy, lower-alkoxy carbonyl or lower-alkoxy-carbonyloxy and said acetyl is optionally substituted with fluoro-lower-alkyl, aryl, lower-alkoxy, hydroxy, lower-alkoxy carbonyl or lower-alkoxy-carbonyloxy;n is 1-4;y is 1-4; andx is 1 or 2in a pharmaceutically acceptable carrier comprising a cellulose derivative.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to x-ray contrast compositions containing iodoaniline derivatives as contrast agents and methods for their use in diagnostic radiology of the gastrointestinal tract.

2. Reported Developments

Roentgenographic examination utilizing X-rays and computed tomography (hereinafter CT) scans of fractures and other conditions associated with the skeletal system is routinely practiced without the use of contrast agents. X-ray visualization of organs containing soft tissue, such as the gastrointestinal (hereinafter GI) tract, requires the use of contrast agents which attenuate X-ray radiation. D. P. Swanson et al in "Pharmaceuticals In Medical Imaging", 1990, MacMillan Publishing Company, provides an excellent background in medical imaging utilizing contrast agents and compositions therewith.

Roentgenographic examination of the GI tract are indicated for conditions of digestive disorders, changes in bowel habit, abdominal pain, GI bleeding and the like. Prior to radiological examination, administration of a radiopaque contrast medium is necessary to permit adequate delineation of the respective lumen or mucosal surface from surrounding soft tissues. Accordingly, a contrast medium is administered orally to visualize the mouth, pharynx, esophagus, stomach, duodenum and proximal small intestine. The contrast medium is administered rectally for examination of the distal small intestine and the colon.

The most widely used contrast agent for the visualization of the GI tract is barium sulfate administered as a suspension orally or rectally as an enema. (See, for example, U.S. Pat. Nos.: 2,659,690; 2,680,089; 3,216,900; 3,235,462; 4,038,379 and 4,120,946) Notwithstanding its relatively good contrast characteristics, negligible absorption from the GI tract following oral or rectal administration and speedy excretion from the body, barium sulfate has certain disadvantages. In the presence of intestinal fluids it lacks homogeneity and poorly adheres to mucus membranes which can result in poor X-ray images. In the colon, when administered as an enema, it flocculates and forms irregular clumps with fecal matter.

Iodinated organic compounds have also been used as GI contrast agents since the iodine atom is an effective X-ray absorber. They have the most versatility and are utilized in the widest variety of procedures. They are very absorptive of X-rays with which the iodine interacts and produce a so-called photoelectric effect which is a large magnification in contrast caused by the photons stopped in the iodine-containing medium. The magnification of contrast exceeds the level that would be expected from relative changes in density. Because of this magnification, relatively low concentrations of the contrast agent can be utilized. (For iodinated agents see, for example, U.S. Pat. Nos.: 2,786,055; 3,795,698; 2,820,814; 3,360,436; 3,574,718, 3,733,397; 4,735,795 and 5,047,228.)

The desiderata for an ideal GI contrast agent includes: good toxicological profile; the ability to fill the entire bowel/lumen and evenly coat the gut mucosa so that the presence of the bowel is detectable when the lumen is not distended; and nonirritation to the intestinal mucosa; and passage through the GI tract without producing artifacts or stimulating vigorous intestinal peristalsis.

These requirements were addressed by many investigators and their efforts resulted in great improvements over the years. The requirement of evenly coating the gut mucosa with a contrast agent to effectively cover the walls of the intestines proved to be rather difficult. Without meeting these requirements it is impossible to obtain X-ray pictures of high precision. To that end, the use of certain polymer additives were proposed as illustrated hereunder.

U.S. Pat. No. 4,069,306 discloses an x-ray contrast preparation which is said to adhere to the walls of body cavities. The preparation comprises a finely divided water-insoluble inorganic x-ray contrast agent and minute particles of a hydrophilic polymer which is insoluble in water but is water-swellable. The body cavity is supplied with such preparation suspended in water. The x-ray contrast agent is present in admixture with and/or enclosed in and/or adhered to said minute polymer particles.

U.S. Pat. No. 4,120,946 discloses a pharmaceutical composition for barium opacification of the digestive tract, comprising colloidal barium sulfate and a polyacrylamide in an aqueous vehicle. The polyacrylamide forms a viscous solution at low concentration which makes it possible to maintain the barium sulfate in suspension and at the same time permit good adherence of the preparation to the walls of the organ which it is desired to x-ray.

U.S. Pat. No. 5,019,370 discloses a biodegradable radiographic contrast medium comprising biodegradable polymeric spheres which carry a radiographically opaque element, such as iodine, bromine, samarium and erbium. The contrast medium is provided either in a dry or liquid state and may be administered intravenously, orally and intra-arterially.

While these polymeric materials greatly enhance attachment of the contrast agent used therewith to the walls of organs for better visualization thereof, there is still a need for an improved X-ray imaging medium that uniformly coats the soft tissues subjected to diagnostic X-ray examination.

We have now discovered that certain iodoaniline derivatives in a pharmaceutically acceptable vehicle comprising a cellulose derivative provides excellent x-ray imaging medium.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide compositions for coating the gastrointestinal tract of mammals to form an effective radiopaque coating thereon by which diagnostic examination of the GI tract may be accomplished.

The object of the present invention is achieved by a composition comprising: an iodoaniline derivative as x-ray contrast agent in a pharmaceutically acceptable vehicle comprising a cellulose derivative.

In accordance with the invention there is further provided a method for x-ray diagnostic imaging of the GI tract which comprises orally or rectally administering to the patient an effective contrast producing amount of the above-described x-ray contrast composition.

The x-ray contrast agent of the present invention is of the formula: ##STR2## or a pharmaceutically acceptable salt thereof wherein Z is H, halo, C.sub.1 -C.sub.20 alkyl, cycloalkyl, lower alkoxy, cyano, where the alkyl and cycloalkyl groups can be substituted with halogen or halo-lower-alkyl groups;

R.sub.1 and R.sub.2 are independently H, C.sub.1 -C.sub.25 alkyl, cycloalkyl, acetyl or halo-lower-alkyl, wherein said C.sub.1 -C.sub.25 alkyl, cycloalkyl and halo lower-alkyl are optionally substituted with fluoro-lower-alkyl, aryl, lower-alkoxy, hydroxy, carboxy, lower-alkoxy carbonyl or lower-alkoxy-carbonyloxy and said acetyl is optionally substituted with fluoro-lower-alkyl, aryl, lower-alkoxy, hydroxy, lower-alkoxy carbonyl or lower-alkoxy-carbonyloxy; n is 1-4; y is 1-4; and x is 1 or 2.

As used herein, the term halogen (or halo) means fluorine, chlorine, bromine or iodine.

As used herein, the term cycloalkyl means carbocyclic rings having from three to eight ring carbon atoms including cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and cyclooctyl which may be substituted on any ring carbon atom thereof by one or more lower-alkyl groups, lower-alkoxy groups or halogens.

As used herein the terms lower-alkyl and lower-alkoxy mean monovalent aliphatic radicals, including branched chain radicals, of from one to ten carbon atoms. Thus, the lower-alkyl moiety of such groups include, for example, methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, t-butyl, n-pentyl, 2-methyl-3-butyl, 1-methylbutyl, 2-methylbutyl, neopentyl, n-hexyl, 1-methylpentyl, 3-methylpentyl, 1-ethylbutyl, 2-ethylbutyl, 2-hexyl, 3-hexyl, 1,1,3,3-tetramethylpentyl, 1,1-dimethyloctyl and the like.

As used herein, the term aryl means an aromatic hydrocarbon radical having six to ten carbon atoms. The preferred aryl groups are phenyl, substituted phenyl and naphthyl substituted by from one to three, the same or different members of the group consisting of lower-alkyl, halogen, hydroxy-lower-alkyl, alkoxy-lower-alkyl and hydroxy.

The x-ray contrast compound can comprise one, two, three or four iodine atoms per molecule; preferred species contain at least two, and more preferably, at least three iodine atoms per molecule.

The solid x-ray contrast agents in particulate forms useful in the practice of the present invention can be prepared by techniques known in the art. The solid agents are comminuted to the desired size using conventional milling methods, such as airjet or fragmentation milling. We have found that an effective average particle size of less than about 100.mu. provides for good distribution and coating in the GI tract. As used herein, particle size refers to a number average particle size as measured by conventional techniques, such as sedimentation field flow fractionation and disk centrifugation. An effective average particle size of less than about 100.mu. means that at least about 90% of the particles have a weight average particle size of less than about 100.mu. as measured by art recognized techniques.

The cellulose derivative utilized in the present invention includes methylcellulose, carboxymethylcellulose, sodium carboxymethylcellulose, hydroxyethyl methylcellulose, hydroxypropyl methylcellulose; and microcrystalline cellulose having an average particle size of from 0.01 to 100.mu., more preferably of from 0.05 to 10.mu., and most preferably of 0.1 to 1 .mu..

The contrast agent and the cellulose derivative are formulated for administration using physiologically acceptable carriers or excipients in a manner within the skill of the art. The contrast agent and the cellulose derivative with the addition of pharmaceutically acceptable aids (such as surfactants and emulsifiers) and excipients are suspended or partially dissolved in an aqueous medium resulting in a dispersion, solution, suspension or emulsion.

A method for diagnostic imaging of the GI tract for use in medical procedures in accordance with this invention comprises orally or rectally administering to the mammalian patient in need of x-ray examination, an effective contrast producing amount of a composition of the present invention. After administration, at least a portion of the GI tract containing the administered composition is exposed to x-rays to produce an x-ray image pattern corresponding to the presence of the contrast agent, then the x-ray image is visualized and interpreted using techniques known in the art.

DETAILED DESCRIPTION OF THE INVENTION

Compounds of the present invention can be made according to the procedure known in the art using commercially available starting materials, intermediates and reagents. Starting materials, reagents and solvents can be obtained from chemical suppliers such as Aldrich, Baker and Eastman Chemical Companies, or they may be prepared by techniques known in the art.

The following examples will further illustrate the compounds used in the present invention.

EXAMPLE 1

N-acetyl-N-2-octyl-4-iodoaniline ##STR3##

A flask containing N-(4'-iodophenyl)-2-amino octane (1.50 g, 4.5 mmol) was charged with acetic acid (15 ml) and acetic anhydride (15 ml). The reaction flask was immersed in an oil bath which was warmed to 70.degree. C. over a period of 0.5 hr. After stirring for 19 hrs, the reaction was allowed to cool, diluted with ether (200 ml), washed with water (2.times.50 ml), saturated aqueous sodium bicarbonate (4.times.50 ml), water (2.times.50 ml) and brine (50 ml), dried (Na.sub.2 SO.sub.4), filtered, and evaporated in vacuo. Flash column chromatography (silica, 1:4; EtOAc:hexanes) provided N-acetyl-N-2-octyl-4-iodoaniline (1.48 g, 70%) as a white solid. Mp 60.degree.-62.degree. C.

Title Compound: .sup.1 H (300 MHz) and .sup.13 C (75 MHz) NMR spectra were consistent with the desired structure. FAB/MS MH.sup.+ 374. Calculated for C.sub.16 H.sub.24 NIO: C, 51.48; H, 6.48; N, 3.75; I, 34.00. Found: C, 51.68, H, 6.46; N, 3.67; I, 33.87.

EXAMPLE 2

N-(4'-iodophenyl)-2-aminooctane ##STR4##

A flask containing 4-iodoaniline (11.0 g, 50.2 mmol) was charged with dry dichloroethane (125 ml), 2-octanone (7.9 ml, 50.0 mmol) and sodium triacetoxyborohydride (13.8 g, 65 mmol). After stirring for 10 minutes, acetic acid (2.9 ml, 50.7 mmol) was added via syringe over a 5 minute period. The reaction was stirred under an N.sub.2 atmosphere for 16 hrs. At the end of this period the reaction was quenched by the careful addition of a solution of saturated aqueous ammonium chloride (100 ml). After stirring for 0.5 hr, the reaction was poured over ether (250 ml) and the layers were separated. The ether layer was washed with saturated aqueous ammonium chloride (100 ml), dried (Na.sub.2 SO.sub.4), filtered and evaporated in vacuo. Flash column chromatography (silica, 1:39; EtOAC:hexanes) provided N-(4'-iodophenyl)-2-aminooctane (14.6 g, 88%) as a light yellow oil.

Title Compound: .sup.1 H (300 MHz) and .sup.13 C (75 MHz) NMR spectra were consistent with the desired structure. Calculated for C.sub.14 H.sub.22 NI: C, 50.97; H, 6.69; I, 38.31. Found: C, 51.19, H, 6.72; I, 37.94.

COMPOSITIONS OF THE PRESENT INVENTION

The contrast agents may be formulated for administration using physiologically acceptable carriers or excipients in a manner within the skill of the art. The compounds with the addition of pharmaceutically acceptable aids (such as surfactants and emulsifiers) and excipients may be suspended or partially dissolved in an aqueous medium resulting in a dispersion, solution or suspension. However, the oily contrast agents are preferably made into emulsions.

Compositions of the present invention comprise the following pharmaceutically acceptable components based on % w/v:

______________________________________ More Most Broad Preferred PreferredIngredients Range Range Range______________________________________Contrast agent 30-200 40-160 85-120(mg I/ml oftotal suspension)Cellulose derivative 0.05-10 0.1-4 0.2-1(% w/v)Oily Vehicle 0.0-55 0.1-25 7-15(% w/v)Surfactant 0.0-20 0.1-10 3-7(% w/v)Viscosity modifying 0.0-15 0.001-4 0.05-1excipients (% w/v)Water - q.s. to 100% by volume______________________________________

When the composition is used for CT imaging of the GI tract, the concentration of the x-ray contrast agent should be in the range of from 0.01 to 40 mg I/ml, more preferably of from 0.25 to 25 mg I/ml and most preferably of from 4-12 mg I/ml.

The preferred cellulose derivative utilized in the present invention is AVICEL.RTM. RC-591, which is a mixture of about 89 parts microcrystalline cellulose and about 11 parts of sodium carboxymethylcellulose.

In further reference to the components used in the compositions of the present invention the following should be noted.

The x-ray contrast agent present in concentrations lower than the above-stated minimum in formulations does not provide good quality x-ray or CT images, while concentrations above the maximum concentration render the GI tract too radiopaque and do not allow sufficient delineation of the GI tract.

In practicing the present invention an oil-in-water emulsion is preferred over a water-in-oil emulsion, suspension and dispersion. Oily materials, the density of which approximate the density of the aqueous phase impart stability to emulsions. For that reason low density oils, such as mineral oils, are desirable in preparing the emulsions. When the x-ray contrast agents are oily substances at room temperature, the presence of an additional oily vehicle is not always necessary. Above about 55% w/v of oil the emulsion is no longer an oil-in-water emulsion but shifts to a water-in-oil emulsion.

Compositions without the presence of surfactants still provide excellent x-ray images, however, without surfactants the compositions are very difficult to emulsify and only suspensions/dispersions are produced which are less desirable for coating the GI tract and are also less stable on shelf-life. For reason of toxicity it is desirable to keep the concentration of certain surfactants as low as possible; above about 20% w/v the risk of toxicity rapidly increases.

While the iodoaniline derivatives of the present invention in formulations with a pharmaceutically acceptable vehicle provide good quality x-ray images, the addition of a cellulose derivative to the formulations greatly increases the quality of the x-ray images. At the low extreme of the concentration range there is little or no benefit gained, while above the higher extreme of the concentration range the emulsion is too viscous for administration.

Depending on the form and amount of cellulose derivative used, additions of viscosity modifying agents may not be necessary; at higher levels than about 15% w/v the viscosity is too high and gels will tend to form.

The following formulation examples will further illustrate the invention

EXAMPLE 3

______________________________________Components Amounts in % w/v______________________________________N-acetyl-N-2-octyl-4-iodoaniline 17.50Light Mineral Oil, NF 12.50Polysorbate 80 (Tween 80) 3.37Sorbitan Mono-oleate (Span 80) 1.64AVICEL .RTM. RC-591 0.50q.s. with water to 100% by volume______________________________________

EXAMPLE 4

______________________________________Components Amounts in % w/v______________________________________N-(4'-iodophenyl)-2-amino octane 25.00(oil at room temperature)Polysorbate 80 (Tween 80) 5.00AVICEL .RTM. RC-591 6.50q.s. with water to 100% by volume______________________________________

As known by those skilled in the art, surfactants or emulsifiers can reduce the interfacial tension between two immiscible phases, i.e., oil-in-aqueous medium. These agents can be used alone or in combination with other emulsifying agents and surfactants. For example, Dow Corning Medical Antifoam AF, which is a composition of 30% w/v polydimethylsiloxane simethicone and silica aerogel, 14% w/v stearate emulsifiers and 0.075% w/v sorbic acid, the balance being water, may be used by itself. Intralipid, which is an emulsion of fatty acids needs the presence of a suspending agent for it to form an acceptable emulsion with contrast agents of the present invention. The surface active agents may be cationic, anionic, nonionic, zwitterionic or a mixture of two or more of these agents.

Suitable cationic surfactants include cetyl trimethyl ammonium bromide. Suitable anionic agents include sodium lauryl sulphate, sodium heptadecyl sulphate, alkyl benzenesulphonic acids and salts thereof, sodium butylnapthalene sulfonate, and sulphosuccinates. Zwitterionic surface active agents are substances that when dissolved in water they behave as diprotic acids and, as they ionize, they behave both as a weak base and a weak acid. Since the two charges on the molecule balance each other out the molecules act as neutral molecules. The pH at which the zwitterion concentration is maximum is known as the isoelectric point. Compounds, such as certain amino acids having an isoelectric point at the desired pH of the formulations of the present invention are useful in practicing the present invention.

In preparing the formulations of the present invention we prefer to use nonionic emulsifiers or surface active agents which, similarly to the nonionic contrast agents, possess a superior toxicological profile to that of anionic, cationic or zwitterionic agents. In the nonionic emulsifying agents the proportions of hydrophilic and hydrophobic groups are about evenly balanced. They differ from anionic and cationic surfactants by the absence of charge on the molecule and, for that reason, are generally less of an irritant than the cationic or anionic surfactants. Nonionic surfactants include carboxylic esters, carboxylic amides, ethoxylated alkylphenols and ethoxylated aliphatic alcohols.

One particular type of carboxylic ester nonionic surface active agents are the partial, for example mono-, esters formed by the reaction of fatty and resin adds, for example of about 8 to about 18 carbon atoms, with polyhydric alcohols, for example glycerol, glycols such as mono-, di-, tetra- and hexaethylene glycol, sorbitan, and the like; and similar compounds formed by the direct addition of varying molar ratios of ethylene oxide to the hydroxy group of fatty acids.

Another type of carboxylic esters is the condensation products of fatty and resin partial acids, for example mono-, esters ethylene oxide, such as fatty or resin acid esters of polyoxyethylene sorbitan and sorbitol, for example polyoxyethylene sorbitan, monotall oil esters. These may contain, for example, from about 3 to about 80 oxyethylene units per molecule and fatty or resin acid groups of from about 8 to about 18 carbon atoms. Examples of naturally occurring fatty acid mixtures which may be used are those from coconut oil and tallow while examples of single fatty acids are dodecanoic add and oleic acid.

Carboxylic amide nonionic surface active agents are the ammonia, monoethylamine and diethylamine amides of fatty acids having an acyl chain of from about 8 to about 18 carbon atoms.

The ethoxylated alkylphenol nonionic surface active agents include various polyethylene oxide condensates of alkylphenols, especially the condensation products of monoalkylphenols or dialkylphenols wherein the alkyl group contains about 6 to about 12 carbon atoms in either branched chain or particularly straight chain configuration, for example, octyl cresol, octyl phenol or nonyl phenol, with ethylene oxide, said ethylene oxide being present in amounts equal to from about 5 to about 25 moles of ethylene oxide per mole of alkylphenol.

Ethoxylated aliphatic alcohol nonionic surface active agents include the condensation products of aliphatic alcohols having from about 8 to 18 carbon atoms in either straight chain or branched chain configuration, for example oleyl or cetyl alcohol, with ethylene oxide, said ethylene oxide being present in equal amounts from about 30 to about 60 moles of ethylene oxide per mole of alcohol.

Preferred nonionic surface active agents include: sorbitan esters (sold under the trade name Span) having the formula: ##STR5## wherein R.sub.1 =R.sub.2 =OH, R.sub.3 =R for sorbitan monoesters,

R.sub.1 =OH, R.sub.2 =R.sub.3 =R for sorbitan diesters, R.sub.1 =R.sub.2 =R.sub.3 =R for sorbitan triesters, where R= (C.sub.11 H.sub.23) COO for laurate, (C.sub.17 H.sub.33) COO for oleate, (C.sub.15 H.sub.31) COO for palmitate, (C.sub.17 H.sub.35) COO for stearate.

Polyoxyethylene alkyl ethers (i.e. Brijs) having the formula:

CH.sub.3 (CH.sub.2).sub.x (O--CH.sub.2 --CH.sub.2).sub.y OH where (x+1) is the number of carbon atoms in the alkyl chain, typically: ______________________________________12 lauryl (dodecyl)14 myristyl (tetradecyl)16 cetyl (hexadecyl)18 stearyl (octadecyl)______________________________________ and y is the number of ethylene oxide groups in the hydrophilic chain, typically 10-60.

Polyethylene sorbitan fatty acid esters, sold under the trade names of Polysorbates 20, 40, 60, 65, 80 & 85, having the formulas (1) and (2) ##STR6## wherein w+x+y+z=20 (Polysorbate 20, 40, 60, 65, 80 and 85)

w+x+y+z=5 (Polysorbate 81) w+x+y+z=4 (Polysorbate 21 and 61).

Polyethylene stearates, such as:

poly(oxy-1,2-ethanediyl),.alpha.-hydro-.omega.-hydroxyoctadecanoate; polyethylene glycol monostearate; and poly(oxy-1,2-ethanediyl)-.alpha.-(1-oxooctadecyl)-.omega.-hydroxy-polyethylene glycol monostearate.

The dosages of the contrast agent used according to the method of the present invention will vary according to the precise nature of the contrast agent used. Preferably, however, the dosage should be kept as low as is consistent with achieving contrast enhanced imaging. By employing as small amount of contrast agent as possible, toxicity potential is minimized. For most contrast agents of the present invention dosages will be in the range of from about 0.1 to about 16.0 g iodine/kg body weight, preferably in the range of from about 0.5 to about 6.0 g iodine/kg of body weight, and most preferably, in the range of from about 1.2 to about 2.0 g iodine/kg body weight for regular x-ray visualization of the GI tract. For CT scanning, the contrast agents of the present invention will be in the range of from about 1 to about 600 mg iodine/kg body weight, preferably in the range of from about 20 to about 200 mg iodine/kg body weight, and most preferably in the range of from about 40 to about 80 mg iodine/kg body weight.

The concentration of the contrast agent should be in the range of from about 0.001% w/v to about 75% w/v of the formulation, preferably from about 0.05% w/v to about 50% w/v and most preferably of from about 0.1% w/v to about 20% w/v.

The invention having been fully described, it will be apparent to one skilled in the art that changes and modifications can be made thereto without departing from the spirit and scope thereof.

Claims

1. An x-ray contrast composition for oral or retrograde examination of the gastrointestinal tract comprising:

(a) from about 0.01 to 200 mg of iodine per ml of the composition of an x-ray contrast producing agent having the formula, or a pharmaceutically acceptable salt thereof ##STR7## wherein Z is H, halo, C.sub.1 -C.sub.20 alkyl, cycloalkyl, lower alkoxy, cyano, where the alkyl and cycloalkyl groups can be substituted with halogen or halo-lower-alkyl groups;

R.sub.1 and R.sub.2 are independently H, C.sub.1 -C.sub.25 alkyl, cycloalkyl, acetyl or halo-lower-alkyl, wherein said C.sub.1 -C.sub.25 alkyl, cycloalkyl and halo lower-alkyl are optionally substituted with fluoro-lower-alkyl, aryl, lower-alkoxy, hydroxy, carboxy, lower-alkoxy carbonyl or lower-alkoxy-carbonyloxy and said acetyl is optionally substituted with fluoro-lower-alkyl, aryl, lower-alkoxy, hydroxy, lower-alkoxy carbonyl or lower-alkoxy-carbonyloxy;

n is 1-4;

y is 1-4; and

x is 1 or 2;

(b) from 0.05 to 10% w/v of a cellulose derivative selected from the group consisting of methylcellulose, carboxymethylcellulose, sodium carboxymethylcellulose, hydroxyethyl methylcellulose, hydroxypropyl methylcellulose and microcrystalline cellulose;

(c) from 0 to 55% w/v of an oily vehicle;

(d) from 0 to 20% w/v of a surfactant selected from the group consisting of nonionic, anionic, cationic and zwitterionic surfactants;

(e) from 0 to 15% w/v of a viscosity modifying excipient; and

(f) water to make 100% by volume.

2. The x-ray composition of claim 1 wherein said x-ray contrast producing agent is present in an amount of 30 to 200 mg of iodine per ml of the composition.

3. The x-ray contrast composition of claim 1 wherein said oily vehicle constitutes from 0.1 to 25% w/v of the composition.

4. The x-ray contrast composition of claim 1 wherein said surfactant constitutes from 0.1 to 10% of the composition.

5. The x-ray contrast composition of claim 1 wherein said microcrystalline cellulose has an average particle size of from 0.01 to 100.mu..

6. The x-ray contrast composition of claim 5 wherein said microcrystalline cellulose is about 89 parts microcrystalline cellulose and about 11 parts of sodium carboxymethylcellulose.

7. The x-ray contrast composition of claim 1 wherein said nonionic surface active agent is selected from the group consisting of carboxylic esters, carboxylic amides, ethoxylated alklyphenols and ethoxylated aliphatic alcohols.

8. The x-ray contrast composition of claim 1, wherein said surfactant is sorbitan ester having the formula: ##STR8## wherein R.sub.1 =R.sub.2 =OH, R.sub.3 =R for sorbitan monoesters,

R.sub.1 =OH, R.sub.2 =R.sub.3 =R for sorbitan diesters,

R.sub.1 =R.sub.2 =R.sub.3 =R for sorbitan triesters,

where R=

(C.sub.11 H.sub.23) COO for laurate,

(C.sub.17 H.sub.33) COO for oleate,

(C.sub.15 H.sub.31) COO for palmitate,

(C.sub.17 H.sub.35) COO for stearate.

9. The x-ray contrast composition of claim i wherein said surface active agent is polyoxyethylene alkyl ether having the formula:

CH.sub.3 (CH.sub.2).sub.x (O--CH.sub.2 --CH.sub.2).sub.y OH

where (x+1) is the number of carbon atoms in the alkyl chain from about 12 to about 18 and y is the number of ethylene oxide groups in the hydrophilic chain from about 10 to about 60.

10. The x-ray contrast composition of claim 1 wherein said surfactant is polyoxyethylene sorbitan fatty acid ester of the formulas (1) and (2) ##STR9## wherein w+x+y+z =20

w+x+y+z =5

w+x+y+z =4.

11. An x-ray contrast composition for oral or retrograde examination of the gastrointestinal tract comprising:

(a) from about 85 to 120 mg of iodine per ml of the composition of an x-ray contrast producing agent having the formula, or pharmaceutically acceptable salt thereof ##STR10## wherein Z is H, halo, C.sub.1 -C.sub.20 alkyl, cycloalkyl, lower alkoxy, cyano, where the alkyl and cycloalkyl groups can be substituted with halogen or halo-lower-alkyl groups;

R.sub.1 and R.sub.2 are independently H, C.sub.1 -C.sub.25 alkyl, cycloalkyl, acetyl or halo-lower-alkyl, wherein said C.sub.1 -C.sub.25 alkyl, cycloalkyl and halo lower-alkyl are optionally substituted with fluoro-lower-alkyl, aryl, lower-alkoxy, hydroxy, carboxy, lower-alkoxy carbonyl or lower-alkoxy-carbonyloxy and said acetyl is optionally substituted with fluoro-lower-alkyl, aryl, lower-alkoxy, hydroxy, lower-alkoxy carbonyl or lower-alkoxy-carbonyloxy;

n is 1-4;

y is 1-4; and

x is 1 or 2;

(b) from 0.2 to 1% w/v of a cellulose derivative selected from the group consisting of methylcellulose, carboxymethylcellulose, sodium carboxymethylcellulose, hydroxyethyl methylcellulose, hydroxypropyl methylcellulose and microcrystalline cellulose;

(c) from 7 to 15% w/v of a mineral oil;

(d) from 3 to 7% w/v of a surfactant selected from the group consisting of nonionic, anionic, cationic and zwitterionic surfactants;

(e) from 0.05 to 1% w/v of a viscosity modifying excipient; and

(f) water to make 100% by volume.

12. The x-ray contrast composition of claim 11 wherein the average particle size of said microcrystalline cellulose is from 0.05 to 10.mu..

13. The x-ray contrast composition of claim 11 wherein said composition is in the form of an oil-in-water emulsion.

14. A method of carrying out x-ray examination of the gastrointestinal tract of a patient, said method comprises the oral or rectal administration to the patient an x-ray contrast formulation comprising:

(a) from about 0.01 to 200 mg of iodine per ml of the composition of an x-ray contrast producing agent having the formula, or a pharmaceutically acceptable salt thereof ##STR11## wherein Z is H, halo, C.sub.1 -C.sub.20 alkyl, cycloalkyl, lower alkoxy, cyano, where the alkyl and cycloalkyl groups can be substituted with halogen or halo-lower-alkyl groups;

R.sub.1 and R.sub.2 are independently H, C.sub.1 -C.sub.25 alkyl, cycloalkyl, acetyl or halo-lower-alkyl, wherein said C.sub.1 -C.sub.25 alkyl, cycloalkyl and halo lower-alkyl are optionally substituted with fluoro-lower-alkyl, aryl, lower-alkoxy, hydroxy, carboxy, lower-alkoxy carbonyl or lower-alkoxy-carbonyloxy and said acetyl is optionally substituted with fluoro-lower-alkyl, aryl, lower-alkoxy, hydroxy, lower-alkoxy carbonyl or lower-alkoxy-carbonyloxy;

n is 1-4;

y is 1-4; and

x is 1 or 2;

(b) from 0.05 to 10% w/v of a cellulose derivative selected from the group consisting of methylcellulose, carboxymethylcellulose, sodium carboxymethylcellulose, hydroxyethyl methylcellulose, hydroxypropyl methylcellulose and microcrystalline cellulose;

(c) from 0 to 55% w/v of an oily vehicle;

(d) from 0 to 20% w/v of a surfactant selected from the group consisting of nonionic, anionic, cationic and zwitterionic surfactants;

(e) from 0 to 15% w/v of a viscosity modifying excipient; and

(f) water to make 100% by volume.

15. The method of claim 14 wherein said x-ray producing agent is N-acetyl-N-2-octyl-4-iodoaniline or N-(4'-iodophenyl)-2-amino octane.