WO1994005336A1

WO1994005336A1 - Film-forming x-ray contrast compositions

Info

Publication number: WO1994005336A1
Application number: PCT/US1993/007900
Authority: WO
Inventors: Carl R. Illig; John L. Toner; Eugene R. Cooper
Original assignee: Sterling Wintrop Inc.
Priority date: 1992-09-01
Filing date: 1993-08-23
Publication date: 1994-03-17
Also published as: AU5086793A; EP0658121A1; MX9305314A; JPH08500604A; IL106848A0

Abstract

Disclosed are x-ray contrast compositions for oral or retrograde examination of the gastrointestinal tract comprising a polymeric material capable of forming a coating on the gastrointestinal tract and a barium salt in a pharmaceutically acceptable carrier; and methods for their use in diagnostic radiology of the gastrointestinal tract.

Description

FILM-FORMING X-RAY CONTRAST COMPOSITIONS.

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This is a continuation-in-part of Appliction Serial Number 07/877,690 filed on May 1, 1992.

BACKGROUND OF THE INVENTION

1 0

Field of the Invention

This invention relates to an x-ray contrast composition for oral or retrograde administration to a mammal comprising a barium salt as the

1 5 contrast producing agent and a polymeric film-forming material.

Reported Developments

Roentgenographic examination utilizing x-rays and computed

20 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

2 5 "Pharmaceuticals In Medical Imaging", 1990, MacMillan Publishing

Company, provides an excellent background in medical imaging utilizing contrast agents and compositions therewith.

The desiderata for an ideal GI contrast agent includes: good

3 0 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; palatability and nonirritation to the intestinal mucosa; and passing through the GI tract without producing artifacts or stimulating vigorous intestinal peristalsis. 3 5 The most widely used contrast agents 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. Patent 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 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. The prior art considers as a serious problem the difficulty in achieving uniform adherence to, and coating of, the mucosa of the GI tract by the water insoluble barium sulfate to provide high quality x- ray photographs. As a result of inadequate adherence to, and non-uniform coating of the mucosa, the x-ray results are often inferior, misleading to the practitioner and the imaging process must be repeated. It has also been observed that the barium sulfate, and other solid inorganic particulate radiopaque agents tend to settle out in the patient after evacuation but before and during x-ray imaging, which again deleteriously affects the quality of the x-ray pictures.

These drawbacks were addressed by many investigators and their efforts resulted in great improvements over the years. The drawbacks of uneven coating of the mucosa by an x-ray contrast composition and insufficient adherence to the mucosa proved to be rather difficult to solve. To that end, the use of certain polymer additives were proposed as illustrated hereunder.

U.S. Patent 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. Patent 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. Patent 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, they do not provide a uniform coating thereon. As such, 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 good adherence to, and uniform coating of the mucosa of the intestine can be obtained by a barium salt in combination with a film-forming material to provide high quality x-ray results.

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. To that end, a thin coating is formed on the inner surface of the GI tract effected by ingesting, prior to visualization by an x- ray emitting device, a polymeric film former, which has incorporated therein a barium salt, capable of coating the GI tract. The removal of the coating occurs as a result of the normal turnover of cells, that is, within about 24 to 48 hours. Such compositions must meet several requirements: the film former must be nontoxic; must not contain leachable or digestible components that would deleteriously affect the patient; and the composition must be capable of forming a film in the pH range of from about 5 to about 8.

The object of the present invention is achieved by a composition comprising: a barium salt; a polymeric material which is at least partially water soluble and contains polarizable or ionizable groups; and a divalent metal ion selected from the group consisting of Mg⁺⁺, Ca⁺⁺, Zn⁺⁺ and Ba⁺⁺ which potentiates the effect of the polymeric material as a film former on the mucosa of the GI tract.

The barium salt, the polymeric film former and the divalent metal ion are incorporated in a solid or liquid media for administration to a mammal for x-ray visualization of the GI tract.

The preferred x-ray contrast agent utilized in the present invention is barium sulfate which is a white, radiopaque, crystalline powder that is essentially insoluble in water. It is commercially available in the particle size range of 0.001 to 0.1 micron diameter. However, good results are obtainable with other finely-divided, inorganic, essentially water-insoluble salts of barium including barium hexaboride, barium chromite, barium fluogallate, barium tri-ortho phosphate, barium metasilicate, barium titanate, barium zirconate and zirconium oxide. The compositions of the present invention contain from about 5% w/w to about 95% w/w of the barium salt. The compositions may be in the form of solids, dispersions, colloids or suspensoids, however, we prefer to use colloids as the preferred embodiment.

DETAΠ ,FD DESCRIPTION OF THE INVENTION

Starting materials, reagents and solvents can be obtained from chemical suppliers, such as Aldrich, Baker and Eastman Chemical Companies; alternatively, they may be prepared by techniques known in the prior art.

The polymers that were found to be suitable for forming a thin coating on the GI tract can be classified as anionic, cationic and neutral polymers, a description of which follows. U. S. Patent No. 4,623,539, the disclosure of which is incorporated by reference, pertains to such polymers.

The barium salt is incorporated in the polymeric material along with the divalent cation by any suitable techniques, such as by mixing, blending, precipitating or by enclosing the contrast agent into minute polymeric particles.

The barium salt, polymeric material and divalent cation blend is then formulated for administration using physiologically acceptable carriers or excipients in a manner within the skill of the art. The barium salt, with the addition of pharmaceutically acceptable aids (such as surfactants and emulsifiers) and excipients, may be suspended in an aqueous medium resulting in a dispersion, suspension or colloid. Alternatively, the barium salt, polymeric material and divalent cation may be formulated into a solid form, such as tablets or capsules.

Solid compositions of the present invention shall contain, instead of surfactants/emulsifiers and water used in the liquid compositions, bulking agents and other pharmaceutically acceptable ingredients advantageously employed to render the compositions palatable.

When the x-ray composition is formulated as a tablet, the bulking agent should have good compression characteristics. Suitable bulking agents are well known in the art and include a sweetener such as sugars, e.g. sucrose, and polyhydric alcohols, e.g. mannitol, sorbitol and xylitol, and mixtures thereof. When formulated as a tablet, it is preferable to incorporate in the composition one or more tablet lubricating agents, such as stearic acid, magnesium stearate and talc. The amount of the tablet lubricating agents as well as any other ingredients required to easily prepare the solid compositions, can readily be determined by the skilled formulator. The solid compositions may have incorporated therein optional pharmaceutically acceptable ingredients in order to impart thereto additional desirable properties, such as flavorants and colorants.

Compositions

Liquid compositions of the present invention comprise the following pharmaceutically acceptable components based on % w/w:

Polymeric Material 0.001 - 25

Divalent Cation 0.001 - 20

Barium Salt 5 - 95

Excipient 0 - 20 Aids (Surfactants/Emulsifiers) 0.01 - 20

Water q.s. to 100

Solid compositions of the present invention comprise the following pharmaceutically acceptable components based on % w/w:

Polymeric Material 0.001 - 25

Divalent Cation 0.001 - 20

Barium Salt 5 - 95 Balking Agent/Lubricant/Flavor q.s. to 100

Excipients advantageously used in the formulations include viscosity mediating and stabilizing agents, such as macrocrystalline cellulose, ethylcellulose, hydroxypropyl methylcellulose and gum arabic. Physiologically acceptable substances may also be included, such as sodium citrate, sodium chloride, therapeutic substances, antacid substances and flavoring agents. The inclusion of antimicrobial/antiseptic agents such as methyl parahydroxybenzoate, ethyl parahydroxybenzoate, propyl parahydroxy-benzoate, benzoic acid, benzyl alcohol, phenol, sodium benzoate, EDTA or sorbic acid may also be desirable in some formulations.

Surfactants or emulsifiers 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 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 amount of such surfactants may be in the range of from 0.01 to 20% w/w of the aqueous formulations, although the amount, in general, is kept as low as possible, preferably in the range of 0.05 to 5% w/w. 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 they 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 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 acids, for example of about 8 to about 18 carbon atoms, with polyalcohols, 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, mono-tall 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 acid and oleic acid.

Carboxylic amide nonionic surface active agents are the ammonia, monoethylamine and diethylamides 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 mono-alkylphenols 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:

(a) Sorbitan esters (sold under the trade name Span) having the formula:

CH₂-R₃ wherein

R_j = R₂ = OH, R₃ = R for sorbitan monoesters, Rj = OH, R₂ = R₃ = R for sorbitan diesters,

R_j = R₂ = R₃ = R for sorbitan triesters, where R = (C_nH₂₃) COO for laurate, (C₁₇H₃₃) COO for oleate, (C₁₅H₃₁) COO for palmitate, (C₁7H₃5) COO for stearate; (b) Polyoxyethylene alkyl ethers (i.e. Brijs) having the formula:

CH₃(CH₂)_x(O-CH₂-CH₂)_yOH where (x + 1) is the number of carbon atoms in the alkyl chain, typically:

and y is the number of ethylene oxide groups in the hydrophilic chain, typically 10-60;

(c) Polyoxyethylene sorbitan fatty acid esters, sold under the trade names of Polysorbates 20, 40, 60, 65, 80 & 85; and

(d) Polyoxyethylene stearates, such as:

poly(oxy-1.2-ethanediyl),α-hydro-ω-hydroxy-octadecanoate; polyethylene glycol monostearate; and poly(oxy-l,2-ethanediyl)-α--(l-oxooctadecyl)-ω-hydroxy- polyethylene glycol monostearate.

The film former polymeric materials used in accordance with the present invention include anionic polymers, cationic polymers and neutral polymers.

I . Anionic Polymers

The anionic polymers carry negative charges in the ionized form and are capable of binding to cell surfaces mainly by electrostatic forces. Suitable anionic polymers include the following: 0 0 0

II II II

R— 0-S — 0 — M⁺⁺ R — C — 0 — M⁺⁺ R— 0— R — C — O — M⁺⁺ II 0 wherein

R is the polymeric chain;

0 0

II

^■0— S — O — and C — 0 — are anionic ligands; and 0

M⁺⁺ is a divalent cation.

Specific anionic polymers useful in the practice of the present invention include:

(1) Sulfated polysaccharides of the formula:

0

II R— 0-S — 0 — M⁺⁺ II 0 wherein R is 3,6-anhydro-D-galactose linked through C-4 to D-galactose; (kappa carrageenan) α-D-galactose units (1-3) linked; (lambda carrageenan) D-galactose

3,6-anhydro-D-galactose; (iota carrageenan) D-galactose

3,6-anhydro-L-galactose: (Agar - Agar) D-galactose

3,6-anhydro-D-galactose; (Furcellaren) D-glucopyranose; (Laminarin sulfate) Galactan; and (Galactan sulfate)

Galactosamino-glucuronans (Chondroitin sulfates); and

M⁺⁺ is Mg+⁺, Ca⁺⁺, Zn⁺⁺, Ba⁺⁺ or mixtures thereof. (2) Carboxylated polysaccharides of the formula:

0

II — C — 0 — M⁺⁺

wherein R is D-galacturonoglycan; and (Pectin) anhydro-D-mannuronic acid and anhydro-L-guluronic acid (Algin) residues; and

M⁺⁺ is Mg⁺⁺, Ca⁺⁺, Zn⁺⁺, Ba⁺⁺ or mixtures thereof.

(3) Cellulose derivatives of the formulae:

O 0 0

II II II

R — O— R— 0— S — O — M⁺⁺ R — O — C — R— O— S — O — M⁺⁺ and

II ' II

0 o

o

II R"— C— R — C — O — M⁺⁺

wherein R is an anhydroglucose residue;

R' is CH₃, C₂H₅ or C₃H₇; R" is CH3 or C2H5; and

M⁺⁺ is Mg⁺⁺, Ca⁺⁺, Zn⁺⁺, Ba⁺⁺ or mixtures thereof.

Examples of cellulose derivatives include: sodium ethylcellulose sulfate, sodium cellulose acetate sulfate and sodium carboxymethyl cellulose. (4) Sulfated, sulfonated or carboxylated synthetic polymers of the formula:

0 o 0

II II II R-S — 0 — M⁺ R— O-S- -0 — M⁺⁺ and R — C — 0 — M⁺⁺ II II o 0

wherein

R is an aliphatic or aromatic hydrocarbon, such as polystyrene, poly(sulfon) resin or carboxylated (poly) vinyl; and

M⁺⁺ is Mg⁺⁺, Ca⁺⁺, Zn⁺⁺, Ba⁺⁺ or mixtures thereof.

I I Cationic Polymers

The cationic polymers carry positive charges in the ionized form. Suitable polymers for practicing the present invention include: dermatan sulfate, keratosulfate, hyaluronic acid, heparin and chitin.

Il l Neutral Polymers

Neutral polymers having polarizable electrons such as oxygen, nitrogen, sulfur, fluoride, chloride, bromide and iodide are also suitable for practicing the present invention. In the presence of a cation, such as Mg⁺⁺, Ca⁺⁺, Zn⁺⁺ or Ba⁺⁺, the polymers are partially polarized thereby providing intermolecular interactions between the polymer and the intestinal wall. Examples of these polymers include: (a) Polysaccharides, such as starch, glycogen, glucan, fructans, mannans, galactomannas, glucomannas, galactans, xylans, glycuranans, dextran and starch amylose;

(b) Cellulose derivatives , such as methylcellulose, hydroxyethylcellulose, ethylhydroxyethyl cellulose , hydroxypropyl methylcellulose and hydroxypropyl cellulose; and

(c) Synthetic polymers, such as polyvinylpyrrolidone, polyvinyl alcohol and ethylene oxide polymers.

Exemplary formulations of the present invention are as shown:

Example 1 Barium Sulfate (114 mg Ba ml) 1.94 g (19.4% w/v)

Dow Corning Med. Antifoam AF emulsion 3.50 g (35% w/v)

Galactan sulfate 0.5 g (5% w/v)

Calcium lactate 0.5 g (5% w/v)

Purified Water q. s. to 10 ml

Example 2

Barium Titanate (114 mg Ba/ml) 1.94 g (19.4% w/v)

Safflower Oil 2.00 g (20% w/v)

Tween-21 0.25 g (2.5% w/v) Hydroxypropyl methylcellulose (4,000 cPs) 2.50 g of 2% solution

Calcium lactate 0.2 g (2% w/v)

Purified Water q. s. to 10 ml

Example 3 Barium Hexaboride (114 mg Ba/ml) 1.68 g (16.8% w/v)

Mineral Oil 0.50 g (5% w/v)

Heparin 0.25 g (2.5% w/v)

Tween-21 0.25 g (2.5% w/v)

Calcium lactate 0.25 g (2.5% w/v) Purified Water q. s. to 10 ml Example 4

Barium Tri-ortho-phosphate (114 mg Ba ml) 1.67 g (16.7% w/v)

Simplesse 100 (Nutrasweet Co.) 3.00 g (30% w/v)

Calcium lactate -0.5 (5% w/v) Hydroxypropyl methylcellulose (4000 cPs) 2.50 g of 2% solution

Purified Water q. s. to 10 ml

The compositions of the invention may be administered orally to the patient for radiological examination of the GI tract. The compositions of the invention may also be administered rectally in the form of enemas to a patient for radiologic examination of the colon.

The dosages of the contrast agent used according to the method of the present invention will vary according to the precise nature of the ingredients used. Preferably, however, the dosage should be kept as low as is consistent with achieving contrast enhanced imaging. By employing as small amount of the composition as possible, toxicity potential is minimized. For most formulations of the present invention dosages will be in the range of from about 0.1 to about 20.0 g Ba/kg body weight, preferably in the range of from about 0.4 to about 8.0 g Ba/kg of body weight, and most preferably, in the range of from about 1.0 to about 3.0 g Ba/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 800 mg Ba kg body weight, preferably in the range of from about 15 to about 250 mg Ba/kg body weight, and most preferably in the range of from about 35 to about 90 mg Ba/kg body weight.

The concentration of the contrast agent should be in the range of from about 5% w/w to about 95% w/w of the formulation, preferably from about 10% w/w to about 60% w/w and most preferably of from about 15% w/w to about 40% w/w.

The concentration of the film forming polymeric material depends on the particular polymer used, however, it should be in the range of 0.001 to about 25% w/w or higher in combination with a divalent substance, such as calcium lactate, having a concentration range of 0.001 to 20% w/w. Dosage level of the polymeric material may be in the range of from about 2 to about 20 g/kg body weight or higher.

The compositions of the present invention possess very good adherence to the walls of the gastrointestinal tract by forming an essentially uniform coating thereon.

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

WHAT IS CLAIMED IS:

1. An x-ray contrast composition for oral or retrograde examination comprising:

a polymeric material capable of forming a coating on the gastrointestinal tract, said polymeric material having atoms containing polarizable electrons thereon, in combination with a divalent cation; and a barium salt in a pharmaceutically acceptable carrier.

2. The x-ray contrast composition of claim 1 wherein said atoms having polarizable electrons are selected from the group consisting of oxygen, nitrogen and sulfur.

3. The x-ray contrast composition of claim 1 wherein said divalent cation is selected from the group consisting of Ca⁺⁺, Mg+⁺, Zn⁺⁺, Ba⁺⁺ and a mixture thereof.

4. The x-ray contrast composition of claim 1 wherein said barium salt is selected from the group consisting of barium sulfate, barium hexaboride, barium chromite, barium fluogallate, barium tri-ortho- phosphate, barium metasilicate, barium titanate, barium zirconate and zirconium oxide.

The x-ray contrast composition of claim 1 wherein said pharmaceutically acceptable carrier is a liquid.

6. The x-ray contrast composition of claim 1 wherein said pharmaceutically acceptable carrier is a solid.

7. The x-ray contrast composition of claim 1 wherein said polymeric material is anionic having the formula: 0 0 o

II II II

R-O-S — 0 — M⁺⁺ R — C — O — M⁺⁺ R-0— R — C — O — M⁺⁺

II o wherein

R is the polymeric chain;

O O 0— S — O — and C — O — are anionic ligands; and

II 0

M⁺⁺ is a divalent cation.

8. The x-ray contrast composition of claim 7 wherein said anionic polymeric material is a sulfated polysaccharide having the formula:

O

II R— 0-S — O — M⁺⁺

II o

wherein R is 3,6-anhydro-D-galactose linked through C-4 to D-galactose; (kappa carrageenan) α-D-galactose units (1-3) linked; (lambda carrageenan) D-galactose 3,6-anhydro-D-galactose; (iota carrageenan) D-galactose

3,6-anhydro-L-galactose: (Agar - Agar) D-galactose

Galactosamino-glucuronans (Chondroitin sulfates); and M⁺⁺ is Mg+⁺, Ca⁺⁺, Zn⁺⁺, Ba⁺⁺ or a mixture thereof.

9. The x-ray contrast composition of claim 7 wherein said anionic polymeric material is a carboxylated polysaccharide having the formula:

O

II R — C — O — M⁺⁺

M⁺⁺ is Mg++, Ca⁺⁺, Zn⁺⁺, Ba⁺⁺ or a mixture thereof.

10. The x-ray contrast composition of claim 7 wherein said anionic polymeric material is a cellulose derivative of the formula:

0 0 0

II II II

R — 0— R— 0— S — O — M⁺⁺ R — O — C — R-0— S — 0 — M⁺⁺ and ii ' ii

0 0

0

II R — C— R — C — O — M⁺⁺

wherein R is an anhydroglucose residue; R is CH₃, C₂H₅ or C₃H₇; R" is CH₃ or C₂H₅; and M++ is Mg++, Ca++, Zn++, Ba⁺⁺ or a mixture thereof.

11. The x-ray contrast composition of claim 10 wherein said cellulose derivative is selected from the group consisting of sodium ethylcellulose sulfate, sodium cellulose acetate sulfate and sodium carboxymethylcellulose.

12. The x-ray contrast composition of claim 7 wherein said anionic polymeric material is a sulfated, sulfonated or carboxylated synthetic polymer having the formula:

O O O

II II II

R-S — O — M⁺⁺ R-O-S — O — M⁺⁺ — R — C — 0 — M ++

0 0

wherein R is an aliphatic or aromatic hydrocarbon; and

M⁺⁺ is Mg⁺⁺, Ca⁺⁺, Zn⁺⁺, Ba⁺⁺ or a mixture thereof.

13. The x-ray contrast composition of claim 1 wherein said polymeric material is cationic selected from the group consisting of: dermatan sulfate, kerato sulfate, hyaluronic acid, heparin and chitin.

14. The x-ray contrast composition of claim 1 wherein said polymeric material is a polysaccharide.

15. The x-ray contrast composition of claim 14 wherein said polysaccharide is selected from the group consisting of starch, glycogen, glucan, fructans, mannans, galactomannans, glucomannas, galactans, xylans, glycuranans, dextran and starch amylose.

16. The x-ray contrast composition of claim 1 wherein said polymeric material is a cellulose derivative.

17. The x-ray contrast composition of claim 16 wherein said cellulose derivative is selected from the group consisting of methylcellulose, hydroxyethyl cellulose, ethylhydroxyethyl and hydroxypropyl cellulose.

18. The x-ray contrast composition of claim 1 wherein said polymeric material is polyvinylpyrrolidone, polyvinyl alcohol or an ethylene oxide polymer.

19. The x-ray contrast composition of claim 1 in an aqueous dispersion.

20. The x-ray contrast composition of claim 1 in the form of a colloid.

21. The x-ray contrast composition of claim 1 wherein said pharmaceutical carrier contains at least one surfactant.

22. The x-ray contrast composition of claim 21 wherein said surfactant is cationic.

23. The x-ray contrast composition of claim 21 wherein said surfactant is anionic.

24. The x-ray contrast composition of claim 21 wherein said surfactant is zwitterionic.

25. The x-ray contrast composition of claim 21 wherein said surfactant is nonionic.

26. The x-ray contrast composition of claim 22 wherein said cationic surfactant is selected from the group consisting of cetyl trimethyl ammonium bromide and dodecyl dimethyl ammonium bromide.

27. The x-ray contrast composition of claim 23 wherein said anionic surfactant is selected form the group consisting of sodium lauryl sulfate, sodium heptadecyl sulphate, an alkyl benzene sulphonic acid, sodium butylnaphthalene sulfonate and sulphosuccinate.

28. The x-ray contrast composition of claim 25 wherein said nonionic surfactant is selected from the group consisting of carboxylic esters, carboxylic amides, ethoxylated alkylphenols and ethoxylated aliphatic alcohols, sorbitan esters, polyoxyethylene alkyl ethers and polyoxyethylene sorbitan fatty acid esters.

29. The x-ray contrast composition of claim 1 further comprising a suspending agent.

30. The x-ray contrast composition of claim 1 further comprising a stabilizer.

31. The x-ray contrast composition of claim 1 further comprising an antioxidant.

32. The x-ray contrast composition of claim 1 further comprising an osmolality adjusting agent.

33. The x-ray contrast composition of claim 1 further comprising a buffering agent.

34. The x-ray contrast composition of claim 1 further comprising a pH adjusting agent.

35. The x-ray contrast composition of claim 1 further comprising a flavoring agent.

36. An orally/rectally administrable x-ray contrast composition for x-ray examination of the gastrointestinal tract comprising an effective contrast-producing amount of barium sulfate;

a polymeric material capable of forming a coating on the gastrointestinal tract, said polymeric material having atoms containing polarizable electrons thereon in combination with a divalent cation; said barium sulfate forming a colloid in an aqueous medium comprising a surfactant.

37. The x-ray contrast composition of claim 36 wherein said surfactant comprises:

30% w/v poly dimethylsiloxane and silica aerogel, 14% w/v stearate emulsifiers; 0.075% w/v sorbic acid; and

55.925% w/v water.

38. The x-ray contrast composition of claim 37 wherein said surfactant is present from about 0.01% w/v to about 20% w/v in said aqueous formulation.

39. 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 composition comprising:

40. The method of claim 39 wherein said barium salt is selected from the group consisting of barium sulfate, barium hexaboride, barium chromite, barium fluogallate, barium tri-ortho phosphate, barium metasilicate, barium titanate, barium zirconate and zirconium oxide.

41. The method of claim 39 wherein said x-ray contrast composition is in the form of a colloid.

42. The method of claim 41 wherein said colloid contains at least one surfactant.

43. The method of claim 42 wherein said surfactant is cationic.

44. The method of claim 42 wherein said surfactant is anionic.

45. The method of claim 42 wherein said surfactant is zwitterionic.

46. The method of claim 42 wherein said surfactant is nonionic.

47. The method of claim 43 wherein said cationic surfactant is selected from the group consisting of cetyl trimethyl ammonium bromide and dodecyl dimethyl ammonium bromide.

48. The method of claim 44 wherein said anionic surfactant is selected from the group consisting of sodium lauryl sulfate; sodium heptadecyl sulphate, an alkyl benzene sulphonic acid, sodium butylnaphthalene sulfonate and sulphosuccinates.

49. The method of claim 46 wherein said nonionic surface active agent is selected from the group consisting of carboxylic esters, carboxylic amides, ethoxylated alkylphenols and ethoxylated aliphatic alcohols, sorbitan esters, polyoxyethylene alkyl ethers and polyoxyethylene sorbitan fatty acid esters.

50. The method of claim 39 wherein said x-ray contrast composition further comprises a suspending agent.

51. The method of claim 39 wherein said x-ray contrast composition further comprises a stabilizer.

52. The method of claim 39 wherein said x-ray contrast composition further comprises an antioxidant.

53. The method of claim 39 wherein said x-ray contrast composition further comprises an osmolality adjusting agent.

54. The method of claim 39 wherein said x-ray contrast composition further comprises a buffering agent.

55. The method of claim 39 wherein said x-ray contrast composition further comprises a pH adjusting agent.

56. The method of claim 39 wherein said x-ray contrast composition further comprises a flavoring agent.