AU575132B2

AU575132B2 - Preperation of amidinoureas

Info

Publication number: AU575132B2
Application number: AU39926/85A
Authority: AU
Inventors: William Lyon Studt
Original assignee: Rorer International Overseas Inc
Current assignee: Rorer International Overseas Inc
Priority date: 1985-02-15
Filing date: 1985-02-15
Publication date: 1988-07-21
Anticipated expiration: 2005-02-15
Also published as: EP0217787A4; FI864067A0; EP0217787A1; AU3992685A; WO1986004935A1; JPS62501839A; FI864067A; DK489186D0; NO863783L; HUT43034A; NO863783D0; DK489186A

Description

AMIDINOUREA PROCESS AND PHARMACEUTICAL COMPOSITION

Field of the Invention

This invention relates to amidinoureas, improved processes for their preparation, and pharmaceutical compositions.

Reported Developments

The amidinoureas prepared by the present invention have been reported to be effective anti-diarrheal agents. In U.S. Patent No. 4,060,635, amidinourea compounds and a method for the treatment of diarrhea by administering these compounds are described. Methods by which these compounds have been prepared include the following general syntheses.

Condensation of a substituted phenyl isocyanate (prepared from an aniline and phosgene in the customary manner) with guanidine results in a 1-substituted phenyl-3-amidinourea as shown in Scheme I below. It is convenient to carry out the reaction by preparing the isocya nate in the reaction media and then forming guanidine in situ by hydrolyzing guanidine carbonate with base. Condensation of the isocyanate takes place when the guanidine forms and the amidinourea compound results.

The amidinoureas may also be prepared by degradation of the corresponding biguanide as shown in Scheme II below. When a 1-substituted phenylbiguanide compound is hydrolyzed in acid at raised temperature, then the resultant product is 1-substituted phenyl-3-amidinourea.

When it is desired to have R_n substitution, the starting material of course will be an aniline having N-alkyl substitution. Reaction with phosgene results in the carbamoyl chloride which is then reacted with the guanidine to prepare the amidinourea as shown in Scheme III below.

The reported processes for the preparation of these compounds are plagued by the presence of side products which require tedious and expensive additional purification steps.

It has been found surprisingly that a modification of the reported process results in the formation of the desired products as a crystalline precipitate which may be easily and inexpensively separated from the reaction.

It has also been reported that the amidinourea compounds may be formulated into anti-diarrheal compositions. However, it has been found that liquid compositions including the amidinourea compounds degrade over prolonged periods of time, thereby limiting their use.

Summary of the Invention

This invention relates to an improved process for the preparation of a compound of Formula I

comprising the reaction of an isocyanate of Formula II

with a guanidine of Formula III

said guanidine being prepared in situ by the treatment of the salt of Formula IV

with aqueous base, wherein:

X, Y and Z are hydrogen, alkyl, alkoxy, cyano, acyloxy, alkenyl, alkynyl, halo, haloalkyl, haloalkoxy, amino, acyl, carbamoyl, nitro, hydroxy, arylalkoxy or alkylsulfonyl;

R₁, R₂ and R₃ are each independently hydrogen, alkyl, cycloalkyl or aralkyl; or R₂ and R₃ together with the nitrogen atom to which they are attached form a 5, 6, or 7 membered ring which may include 0-2 additional heteroatoms of N, O or S; provided that at least one of R₁, R₂ or R₃ is other than hydrogen; the improvement comprising the use of a ketone as the reaction medium, with a lower alkyl ketone being preferred.

This invention also relates to a method for the preparation of a liquid pharmaceutical composition comprising a compound of Formula I. Detailed Description of the Invention

The process according to this invention comprises the use of a ketone as the reaction medium. It has been found that the use of such reaction medium results in formation of a crystalline precipitate of an amidinourea of Formula I, which can be easily separated and purified for use as a pharmaceutical product. The most desired ketone is acetone, although other lower alkyl ketones such as methylethyl ketone and ethylethyl ketone may be utilized in the reaction process.

The nomenclature applied to the compounds of this invention is as follows.

The term "loweralkyl" refers to an alkyl hydrocarbon group of from 1 to 5 carbon atoms which may be straight chained or branched, while "alkyl" refers to an alkyl hydrocarbon group which may have as many as ten carbon atoms.

The term "cycloalkyl" refers to a cycloalkyl group having 3-7 carbon atoms.

The "loweralkoxy" radical signifies an alkoxy group containing from 1 to about 5 carbon atoms which may be straight chained or branched.

The preferred "aryl" group is phenyl.

The preferred "aralkyl" groups are benzyl and phenethyl. The preferred "halo loweralkyl" group is trifluoromethyl.

The preferred "halo loweralkoxy" group is trifluoromethoxy.

The most preferred process is a process for the preparation of a compound of Formula V

wherein a compound of Formula VI

is added to a reaction solution prepared by mixing a compound of Formula VII

and a neutralizing quantity of aqueous base in a ketone solvent; wherein X and Y are hydrogen, alkyl, halo, alkoxy, haloalkyl or haloalkoxy; and R₂ and R₃ are hydrogen, alkyl, cycloalkyl, aralkyl or alkoxy; provided that at least one of R₂ and R₃ is other than hydrogen. The following is a detailed example which shows the process according to the present invention. This is to be construed as an illustration of this process and not as a limitation thereof.

EXAMPLE PREPARATION OF 1-(2,6- DIMETHYLPHENYD-3-METHYLAMIDINOUREA

736 g of 50% w/w aqueous sodium hydroxide are added to 1,123.6 g of methylguanidine sulfate suspended in 5.2 1 of acetone (reagent grade). The mixture is stirred for 3 hrs. To the rapidly stirred suspension there is added dropwise over a period of 4 hours a mixture of 1,176.0 g of 2,6-dimethylphenylisocyanate and 350 ml of acetone. During the addition a cold water bath is used to maintain the temperature at approximately 25°C, After the addition is complete the reaction mixture is stirred overnight.

The mixture is chilled to 10°C in an ice bath and the solid collected by filtration. The filter cake is washed with 2 1 of cold acetone. The solid is suspended in 4 1 of water and stirred for 30 minutes.

The suspension is filtered and the solid washed on the filter with 4 1 of water. The solid is suspended in 2.5 1 of water at 60°C. 670 ml of concentrated hydrochloric acid are added to the suspension while stirring. After dissolution is complete 360 g of sodium chloride (USP--crystal) is added in portions. Using a water bath the mixture is cooled to 18°C over a period of 1 hr. The suspension is filtered and the solid washed with 1 1 of a cold 4% solution of sodium chloride in 0.36 molar hydrochloric acid. The material is partially dried on the filter.

An aliquot (100 g) of the filter cake is removed to prepare a final wash solution. This aliquot is dissolved in 800 ml of water, the solution is filtered and diluted to 1 1. The solution is stored at 5°C until the bulk of the material is processed as follows: The remainder of the filter cake is dissolved in 2.5 1 of water (60°C) and the solution is filtered. 250 ml of concentrated hydrochloric acid are added to the stirred filtrate at 35°C which induces crystallization. 218 g of sodium chloride (USP--crystal) are added to the stirred suspension in portions. The mixture is stirred for 1 hr. while a cold water bath is used to reduce the temperature to 18°C. The suspension is filtered and the solid washed with 2 1 of a cold 4% solution of sodium chloride in 0.36 molar hydrochloric acid and then with the 1 1 of cold wash solution prepared above. The solid is left on the filter until no additional filtrate can be collected. The filter cake is spread on a tray and dried at 50°C in a mechanical convection oven for 24 hrs. This yields 1480.3 g of 1-(2,6-dimethylphenyl)-3-methyl amidinourea hydrochloride, M.P. 200-203°C.

The dried product is examined by TLC (1:1, CHCl₃: EtOCHO, Silica). The presence of mobile materials (R_f>0.1) requires that the product be washed with methylene chloride as follows:

1-(2,6-dimethylphenyl)-3-methylamidinourea hydrochloride (1,267 g, greater than 0.1% N,N"-bis (2,6-dimethyIphenylcarbamoyl)-N'-methylguanidine hydrochloride) is suspended in 2,534 ml of methylene chloride at RT and stirred for 2 hrs. The suspension is filtered and the filter cake is washed with 2 1 of methylene chloride. The solid is air dried to obtain 1 ,194 g (94.2%) of 1-(2,6-dimethylphenyl)-3-methylamidinourea hydrochloride, M.P. 200-203°C. TLC (1:1, CHCl₃: EtOCHO, Silica) shows no mobile materials. The product obtained by this procedure can be precipitated further from aqueous hydrochloric acid - sodium chloride if desired. When 2,6-dimethylphenyl isocyanate is replaced by one of the isocyanates of Table I below, then the corresponding product of Table II is prepared when reacted with methylguanidine.

TABLE I

2-methyl-6-chlorophenylisocyanate

2-methyl-6-fluorophenylisocyanate

2-methyl-6-bromophenylisocyanate

2-methyl-6-iodophenylisocyanate

2-methyl-6-methoxyphenylisocyanate

2-methyl-6-ethoxyphenylisocyanate

2-methyl-6-ethylphenylisocyanate

2-methyl-6-propylphenylisocyanate

2-methyl-6-i-propylphenylisocyanate

2-methyl-6-butylphenylisocyanate

2-methyl-6-cyanophenylisocyanate

2-methyl-6-trifluoromethylphenylisocyanate

2-methyl-6-nitrophenylisocyanate

2-methyl-6-methylsuIfonylphenylisocyanate

2-ethyl-6-chlorophenylisocyanate

2-ethyl-6-fluorophenylisocyanate

2-ethyl-6-bromophenylisocyanate

2-ethyl-6-methoxyphenylisocyanate

2-ethyl-6-ethoxyphenylisocyanate

2,6-diethylphenylisocyanate

2-ethyl-6-propylphenylisocyanate

2-ethyl-6-trifluoromethylphenylisocyanate

2-propyl-6-chlorophenylisocyanate

2-propyl-6-fluorophenylisocyanate

2-propyl-6-bromophenylisocyanate 2-propyl-6-methoxyphenylisocyanate 2-propyl-6-ethoxyphenylisocyanate 2,6-dipropylphenylisocyanate 2-i-propyl-6-chloroρhenylisocyanate 2-i-propyl-β-fluorophenylisocyanate 2-i-propyl-6-methoxyphenylisocyanate 2-butyl-6-chlorophenylisocyanate 2,6-dichlorophenylisocyanate 2-chloro-6-fluorophenylisocyanate 2,6-difluorophenylisocyanate 2,4,6-trimethylρhenylisocyanate 2,4-dimethyl-6-ethylphenylisocyanate 2,4-dimethyl-6-chlorophenylisocyanate 2,4-dimethyl-6-bromoρhenylisocyanate 2,4-dimethyl-6-fluorophenylisocyanate 2,4-dimethyl-6-trifluorophenylisocyanate 2,4-dimethyl-6-nitrophenylisocyanate 2,4-dimethyl-6-methoxyphenylisocyanate 2,6-dimethyl-4-ethylphenylisocyanate 2,6-dimethyl-4-chlorophenylisocyanate 2,6-dimethyl-4-bromophenylisocyanate 2,6-dimethyl-4-fluorophenylisocyanate 2,6-dimethyl-4-methoxyphe'nylisocyanate 2-methyl-4,6-dichlorophenylisocyanate 2-methyl-4,6-difluorophenylisocyanate 2-methyl-4-fluoro-6-bromophenylisocyanate 2-methyl-4-fluoro-6-chlorophenylisocyanate 2-methyl-4-bromo-6-chloroρhenylisocyanate 2-methyl-4-chloro-6-fluorophenylisocyanate 2-methyl-4-chloro-6-bromophenylisocyanate 2-methyl-4-methoxy-6-chlorophenylisocyanate 2-methyl-4-ethyl-6-chlorophenylisocyanate 2-methyl-4-chloro-6-trifluoromethylphenylisocyanate 2-methyl-4-trifluormethyl-6-chlorophenylisocyanate

2-ethyl-4,6-dichlorophenylisocyanate

2-ethyl-4,6-difluorophenylisocyanate

2-ethyl-4-fluoro-6-bromophenylisocyanate

2-ethyl-4-fluoro-6-chlorophenylisocyanate

2-ethyl-4-bromo-6-chlorophenylisocyanate

2-ethyl-4-chloro-6-fluorophenylisocyanate

2-ethyl-4-chloro-6-bromophenylisocyanate

2,6-diethyl-4-chlorophenylisocyanate

2,6-diethyl-4-bromophenylisocyanate

2,6-diethyl-4-fluorophenylisocyanate

2,4-dimethyl-6-nitroρhenylisocyanate

TABLE II

1-(2-methyl-6-chlorophenyl)-3-methylamidinourea

1-(2-methyl-6-fluorophenyl)-3-methylamidinourea

1-(2-methyl-6-bromophenyl)-3-methylamidinourea

1-(2-methyl-6-iodophenyl)-3-methylamidinourea

1-(2-methyl-6-methoxyphenyl)-3-methylamidinourea

1-(2-methyl-6-ethoxyphenyl)-3-methylamidinourea

1-(2-methyl-6-ethylphenyl)-3-methylamidinourea

1-(2-methyl-6-propylphenyl)-3-methylamidinourea

1-(2-methyl-6-i-propylphenyl)-3-methylamidinourea

1-(2-methyl-6-butylphenyl)-3-methylamidinourea

1-(2-methyl-6-cyanophenyl)-3-methylamidinourea

1-(2-methyl-6-trifluoromethylphenyl)-3-methylamidinourea

1-(2-methyl-6-nitrophenyl)-3-methylamidinourea

1-(2-methyl-6-methylsulfonylphenyl)-3-methylamidinourea

1-(2-ethyl-6-chlorophenyl)-3-methylamidinourea

1-(2-ethyl-6-fluorophenyl)-3-methylamidinourea 1-(2-ethyl-6-bromophenyl)-3-methylamidinourea 1-(2-ethyl-6-methoxyphenyl)-3-methylamidinourea 1-(2-ethyl-6-ethoxyphenyl)-3-methylamidinourea 1-(2,6-diethylphenyl)-3-methylamidinourea 1-(2-ethyl-6-propylphenyl)-3-methylamidinourea 1-(2-ethyl-6-trifluoromethylphenyl)-3-methylamidinourea 1-(2-propyl-6-chlorophenyl)-3-methylamidinourea 1-(2-propyl-6-fluorophenyl)-3-methylamidinourea 1-(2-propyl-6-bromophenyl)-3-methylamidinourea 1-(2-propyl-6-methoxyphenyl)-3-methylamidinourea 1-(2-propyl-6-ethoxyphenyl)-3-methylamidinourea 1-(2,6-dipropylphenyl)-3-methylamidinourea 1-(2-i-propyl-6-chlorophenyl)-3-methylamidinourea 1-(2-i-propyl-6-fluorophenyl)-3-methylamidinourea 1-(2-i-propyl-6-methoxyphenyl)-3-methylamidinourea 1-(2-butyl-6-chlorophenyl)-3-methylamidinourea . 1-(2,6-dichlorophenyl)-3-methylamidinourea 1-(2-chloro-6-fluorophenyl)-3-methylamidinourea 1-(2,6-difluorophenyl)-3-methylamidinourea 1-(2,4,6-trimethylphenyl)-3-methylamidinourea 1-(2,4-dimethyl-6-ethylphenyl)-3-methylamidinourea 1-(2,4-dimethyl-6-chlorophenyl)-3-methylamidinourea 1-(2,4-dimethyl-6-bromophenyl)-3-methylamidinourea 1-(2,4-dimethyl-6-fluorophenyl)-3-methylamidinourea 1-(2,4-dimethyl-6-trifluorophenyl)-3-methylamidinourea 1-(2,4-dimethyl-6-nitrophenyl)-3-methylamidinourea 1-(2,4-dimethyl-6-methoxyphenyl)-3-methylamidinourea 1-(2,6-dimethyl-4-ethylphenyl)-3-methylamidinourea 1-(2,6-dimethyl-4-chlorophenyl)-3-methylamidinourea 1-(2,6-dimethyl-4-bromophenyl)-3-methylamidinourea 1-(2,6-dimethyl-4-fluorophenyl)-3-methylamidinourea 1-(2,6-dimethyl-4-methoxyphenyl)-3-methylamidinourea 1-(2-methyl-4,6-dichlorophenyl)-3-methylamidinourea 1-(2-methyl-4,6-difluorophenyl)-3-methylamidinourea 1-(2-methyl-4-fluoro-6-bromophenyl)-3-methylamidinourea 1-(2-methyl-4-fluoro-6-chlorophenyl)-3-methylamidinourea 1-(2-methyl-4-bromo-6-chlorophenyl)-3-methylamidinourea 1-(2-methyl-4-chloro-6-fluorophenyl)-3-methylamidinourea 1-(2-methyl-4-chloro-6-bromophenyl)-3-methylamidinourea 1-(2-methyl-4-methoxy-6-chlorophenyl)-3-methylamidinourea 1-(2-methyl-4-ethyl-6-chloroρhenyl)-3-methylamidinourea 1-(2-methyl-4-chloro-6-trifluoromethylphenyl)-3-methylamidinourea 1-(2-methyl-4-trifluoromethyl-6-chlorophenyl)-3-methylamidinourea 1-(2-ethyl-4,6-dichlorophenyl)-3-methylamidinourea 1-(2-ethyl-4,6-difluorophenyl)-3-methylamidinourea 1-(2-ethyl-4-fluoro-6-bromophenyl)-3-methylamidinourea 1-(2-ethyl-4-fluoro-6-chlorophenyl)-3-methylamidinourea 1-(2-ethyl-4-bromo-6-chlorophenyl)-3-methylamidinourea 1-(2-ethyl-4-chloro-6-fluorophenyl)-3-methylamidinourea 1-(2-ethyl-4-chloro-6-bromophenyl)-3-methylamidinourea 1-(2,6-diethyl-4-chlorophenyl)-3-methylamidinourea 1-(2,6-diethyl-4-bromophenyl)-3-methylamidinourea 1-(2,6-diethyl-4-fluorophenyl)-3-methylamidinourea 1-(2,4-dimethyl-6-nitrophenyl)-3-methylamidinourea

The isocyanates of Table I may be prepared as described above from the corresponding anilines which are either known, or may be prepared by known techniques. Thus, chlorination or bromination of an acetanilide or aniline may be carried out in acetic acid, or in the presence of a small amount of iodine dissolved in an inert solvent such as carbon tetrachloride. A solution of chlorine or bromine is then added while the temperature is held near 0°C. lodination may also be carried out by known methods using iodine monochloride (Cl I). Alkylation may be carried out on an acetanilide using an alkyl halide and aluminum chloride under Friedel-Crafts conditions to obtain desired alkyl substitution.

Nitration may be carried out using fuming nitric acid at about 0°C.

A nitro compound may be hydrogenated to the corresponding amine which may then be diazotized and heated in an alcohol medium to form the alkoxy compound.

An amino compound may also be diazotized to the diazonium fluoroborate which is then thermally decomposed to the fluoro compound.

Diazotization followed by a Sandmeyer type reaction may yield the bromo, chloro or iodo compound.

When an amino compound is diazotized followed by reaction with potassium ethylxanthate and then hydrolyzed, the mercapto compound results. This in turn may be alkylated to the alkylthio group which is then oxidized to the corresponding alkylsulfonyl substituent.

A chloro, bromo or iodo compound may also be reacted with trifluoromethyliodide and copper powder at about 150°C in dimethylformamide to obtain a trifluoromethyl compound [Tetrahedron Letters: 47,4095 (1959)]. A halo compound may also be reacted with cuprous methanesulfinate in quinoline at about 150°C to obtain a methylsulfonyl compound.

When it is desired that the final product contain a hydroxy group, it is preferred that the starting aniline contain the corresponding acyloxy or aralkyloxy groups. These may be prepared in the usual fashion by acylating the starting hydroxy aniline compound with an acyl halide or anhydride in the presence of a tertiary amine or aralkylating with an aralkyl halide or sulfate. Of course the amine function would be protected in the customary manner. Hydrogenation to the desired hydroxy compound may then take place after the formation of the amidinourea. This may be accomplished with a metal catalyst (Pd/C, Pt etc.) in a polar medium (ethanol, THF, etc.), sodium in liquid ammonia, etc. Thus, for example, the 3,4-dihydroxy amidinourea compound may be prepared from the corresponding 3,4-dibenzyloxyaniline. The hydroxy compounds may also be prepared by hydrolysis of the acyl or alkoxy compounds with acid.

Reactions may also be carried out at other stages of synthesis depending on the substituents present and the substituents desired, and various combinations of the foregoing reactions will be determined by one skilled in the art in order that the desired product results. Thus, a phenylamidinourea may be halogenated or nitrated as above, etc.

The compounds of Formula I are useful anti-diarrheal agents. Various tests can be carried out in animal models to show the ability of the compounds of Formula I to exhibit reactions that can be correlated with anti-diarrheal activity in humans. The following tests show the ability of the compounds of this invention to inhibit diarrhea in animals and are known to correlate well with anti-diarrheal activity in humans. These are considered to be standard tests used to determine anti-diarrhea properties. This correlation can be shown by the activities of compounds known to be clinically active. In view of the results of these tests, the amidinoureas of this invention can be considered to be anti-diarrheal agents.

1. Fecal output in rat.

Ref: - Bass, P., Kennedy, J.A. and Willy, J.N.: Measurement of fecal output in rats. Am. J. Dig. Dis. 10: 925-928, 1972. 2. Castor oil test in mice.

Ref: - Niemegeers, C.J.E., Lenaerts, F.M. and Janssen, P.A.J. Difenoxine, a potent, orally active and safe anti-diarrheal agent in rats. Arzneim-Forscth (Drug Res.) 22, 516-1518, 1972.

The compounds of Formula I may be administered orally, parenterally or rectally. Administration by the oral route is preferred. Orally, these compounds may be administered in tablets, hard or soft capsules, aqueous or oily suspensions, dispersible powders or granules, emulsions, syrups or elixers. The optimum dosage, of course, will depend on the particular compound being used and the type and severity of the condition being treated. In any specific case the appropriate dosage selected will further depend on factors of the patient which may influence response to the drug; for example, general health, age, weight, etc. of the subject being treated.

Although the optimum quantities of the compounds of this invention to be used as anti-diarrheal agents will depend on the compound employed and the particular type of disease condition treated, oral dose levels of preferred compounds when administered to a mammal in dosages of 0.01 to 500 milligrams per kilogram of body weight per day are particularly useful. The preferred range is 0.05 to 200 mg/kg. Comparative dosages may be used in parenteral or rectal administration.

The composition may contain such selected excipients as inert diluents such as calcium carbonate, lactose, etc.;granulating and disintegrating agents such as maize starch, alginic acid, etc.; lubricating agents such as magnesium stearate, etc.; binding agents such as starch gelatin, etc.; suspending agents such as methyl cellulose, vegetable oil, etc.; dispersing agents such as lecithin, etc.; thickening agents such as beewsax, hard paraffin, etc.; emulsifying agents such as naturally-occurring gums, etc.; non-irritating excipients such as cocoa butter, polyethylene glycols, etc.; and the like. Further, in formulating these compounds for every 100 parts by weight of the composition, there nay be present between 5 and 95 parts by weight of the active ingredient. The dosage unit form will generally contain between 0.1 mg and about 500 mg of the active ingredients of this invention. The preferred unit dose is between 1 mg and about 50 mg. The compositions may be taken 1-8 times daily depending on the dosage unit required.

Further the active amidinourea may be administered alone or in admixture with other agents having the same or different pharmacological properties.

The debilitating effects of diarrhea result partially from electrolyte imbalance in the patient, so that it is recommended that a solvent or diluent forming the carrier of the liquid pharmaceutical compositions, whether designed for injection or oral administration, should incorporate electrolyte balance. The precise composition of the electrolyte replenisher incorporated in the liquid compositions will depend on the age and the general health and condition of the patient, but in many cases it is appropriate to use a commercially available electrolyte replenisher. These generally include sodium chloride alone or in combination with potassium salts, calcium salts, lactates or bicarbonates, and typical examples are Ringer's Solution, Darrow's Solution (for injection), Ringer's Injection and Lactated Ringer's Injection. These and other examples of commercially available electrolyte replenishers may be found in the "Pharmacopeia of the United States".

A particularly preferred liquid anti-diarrheal composition is one in which the carrier is a solvent or diluent comprising a saline solution of substantially isotonic concentration.

Liquid compositions for oral use are preferably aqueous, so as to permit the inclusion of an electrolyte. Ingredients suitable for incorporation in the carrier of an aqueous liquid suspension are for example suspending agents such as sodium carboxymethylcellulose, methylcellulose, hydroxypropylmethylcellulose, sodium alginate, polyvinylpyrrolidine, gum tragacanth and gum acacia; dispersing or wetting agents such as a naturally occurring phosphatide, for example lecithin, condensation products of an alkylene oxide with fatty acids, for example polyoxyethylene stearate, condensation products of ethylene oxide with long-chain aliphatic alcohols, for example heptadecaethyleneoxyethanol, condensation products of ethylene oxide with partial esters derived from fatty acids and a hexitol, for example polyoxyethylene sorbitol mono-oleate or condensation products of ethylene oxide with partial esters derived from fatty acids and hexitol anhydrides, for example polyoxyethylene sorbitan mono-oleate. Aqueous suspensions may also in particular contain one or more preservatives, for example ethyl- or n-propyl-p-hydroxybenzoate, one or more colouring agents, one or more flavouring agents, and one or more sweetening agents, such as sucrose.

Oily suspensions may be formulated .by suspending the amidinourea in a vegetable oil, for example arachis oil, olive oil, sesame oil or coconut oil, or in a mineral oil such as liquid paraffin. The oily suspensions may contain a thickening agent, for example beeswax, hard paraffin or cetyl alcohol. Sweetening agents, such as those set forth above, and flavouring agents may here also be added to provide a palatable oral preparation. These compositions may also be preserved by the addition of an anti-oxidant such as ascorbic acid.

Where the liquid compositions are in the form of oil-in-water emulsions, the oily phase may be a vegetable oil, for example olive oil or arachis oil, or a mineral oil, for example liquid paraffin, or mixtures of these. The emulsions may also contain sweetening and flavouring agents.

Syrups and elixirs in particular may be formulated with sweetening agents, for example glycerol, sorbitol or sucrose. Such formulations may also contain a demulcent, a preservative, and flavouring and colouring agents.

The liquid compositions, as hereinbefore described, may be formulated for injection. For example they may take the form of a sterile injectable aqueous suspension formulated according to the known art and containing those suitable dispersing or wetting agents and suspending agents which have been mentioned above. An injectable composition is preferably a sterile injectable solution or suspension of the amidinourea in a parenterally acceptable diluent or solvent, for example a sterile aqueous solution buffered to a pH of 4.0 to 7.0 and made isotonic with sodium chloride.

It has been found that the liquid compositions including an anti-diarrheal composition of Formula I degrade over a period of time. Accordingly, the present invention relates to a method of providing a stable dosage form for preparation into a liquid form immediately prior to its use. More particularly the present invention is a method for the preparation of a liquid pharmaceutical composition suitable for oral administration or parenteral injection, said composition comprising a pharmaceutically acceptable liquid vehicle and from 1 to 25 mg of a compound of the Formula I

wherein X, Y and Z are hydrogen, alkyl, alkoxy, cyano, acyloxy, alkenyl, alkynyl, halo, haloalkyl, haloalkoxy, amino, acyl, carbamoyl, nitro, hydroxy, arylalkoxy or alkylsulfonyl;

R₁, R₂ and R₃ are each independently hydrogen, alkyl, cycloalkyl or aralkyl; or R₂ and R₃ together with the nitrogen atoms to which they are attached form a 5, 6, or 7 membered ring which may include 0-2 additional heteroatoms of N, O or S; provided that at least one of R₁, R₂ or R₃ is other than hydrogen; which method comprises combining the compound of Formula I with the vehicle by the steps of:

(a) dissolving an effective anti-diarrheal dosage amount of a salt of said compound in a liquid vehicle comprising either sterile water or a sterile electrolyte replenisher solution; (b) sterilizing the solution by means of microfiltration; (c) freeze-drying the sterilized solution to form a dessicated composition; and

(d) preparing the liquid composition for administration by dissolving the dessicated composition in a dosage volume of liquid vehicle comprising either sterile water or a sterile electrolyte replenisher solution; the said dosage amount and volume being for either single or multiple doses, and in the latter case a preservative being added in step (a) or step (d).

The following formulations are given in illustration of the compositions prepared from the compounds of Formula I.

Formulation 1.

An aqueous solution for parenteral administration is prepared as follows:

50 g of 1-(2,6-dimethylphenyl)-3-methylamidinourea hydrochloride and 5 g of propyl p-hydroxybenzoate are dissolved and diluted to 5,000 cm³ with twice-distilled water after the addition of modified sorensen buffer solution in an amount sufficient to adjust the pH value to a pH of 6.0. Sodium chloride is dissolved therein in an amount sufficient to render the resulting solution isotonic. The resulting solution is passed through a bacteriological filter, the filtrate distributed to 1000 sterile ampoules, the contents of each ampoule is freezedried and sealed for later use. Reconstitution with 5 cm³ of sterile water results in a parenterally applicable solution which contains 50 mg of 1-(2,6-dimethylphenyl)-3-methylamidinourea hydrochloride in 5 cm³ of the solution. Formulation 2.

A sterilized aqueous solution for oral administration containing 1-(2,6-dimethylphenyl)-3-amidinourea hydrochloride is made up from the following ingredients: 1-(2,62dimethylphenyl)-3- amidinourea hydrochloride 5 mg

Sodium chloride 86 mg

Potassium chloride 3 mg

Calcium chloride 2H₂O 3.3 mg

Deionized water q.v. 100 cm³

Formulation 3.

A sterile solution suitable for interperitoneal injection, containing 10 mg of 1-(2,6-dimethylphenyl)-3-methylamidinourea hydrochloride in each 10 ml (1:1 wt/vol), is prepared from the following ingredients: 1-(2,6-dimethylphenyl)-3- methylamidinourea hyrochloride 10 g Benzyl benzoate 100 cm³

Methylparaben 1 g

Propylparaben 0.5 g

Cottonseed oil q.s. 500 cm³

Formulation 4.

500 ampoules, each with 2 ml of solution containing 15 mg of 1-(2,6-dimethylphenyl)-3-methylamidinourea hydrocloride, are prepared from the following types and amount of materials. 1-(2,6-dimethylphenyl)-3- methylamidinourea hyrochloride 7.5 g

Ascorbic acid 1 g

Sodium bisulphite 0.5 g

Sodium sulphite 1 g

Deionized water q.s. 1000 cm³

Formulation 5.

Tablets of 850 mg are prepared by maximum compression of a mixture of the following ingredients: 1-(2 ,6-dimethylphenyl)-3- methylamidinourea hyrochloride 500 mg Tricalcium phosphate 200 mg

Talc 50 mg

Magnesium stearate 10 mg

Polyvinyl acetate 40 mg

Protective excipients such as ethylcellulose, dibutylphthalate, propylene glycol, wax (white and/or carnauba), spermaceti, methylene chloride and rectified diethyl ether may optionally be included among the ingredients.

Formulation 6.

A lot of tablets, each containing 20 mg of 1-(2,6-dimethylphenyl)-3-methylamidinourea hydrochloride are prepared from the following ingredients: 1-(2,6-dimethylphenyl)-3- methylamidinourea hyrochloride 1 kg Dicalcium phosphate 1 kg

Methylcellulose USP 75 kg

Talc 150 g Cornstarch 200 g

Magnesium stearate 10 g The amidinourea and dicalcium phosphate are mixed thoroughly and granulated with a 7.5% solution of methylcellulose in water and passed through a #8 screen and air-dried. The dried granules are passed through a #12 screen and combined with the talc, starch and magnesium stearate with thorough mixing, after which the composition is compressed into tablets.

Formulation 7:

A lot of two-piece hard gelatin capsules, each containing 25 mg of 1-(2,6-dimethylphenyl)-3-methyl amidinourea hydrochloride, are prepared from the following types and amounts of ingredients: 1-(2,6-dimethylphenyl)-3- methylamidinourea hyrochloride 500 g Dicalcium phosphate 500 g

Talc 150 g

Magnesium stearate 5 g

The ingredients are mixed thoroughly and filled into capsules for oral administration to animals at the rate of about one every four hours. If desired, slow release or delay release forms can be provided, depending on choice of capsules and formulating ingredients.

Formulation 8:

Tablets for oral administration, each containing 25 mg of 1-(2,6-dimethylphenyl)-3-methylamidinourea hydrochloride, are prepared from a mixture of the following ingredients:

1-(2,62dimethylphenyl)-3- methylamidinourea hyrochloride 500 g Lactose USP 350 g

Potato starch USP 346 g The mixture is moistened with an alcoholic solution of 20 g of stearic acid and granulated through a sieve. After drying, the following ingredients are added:

Potato starch USP 320 g

Talc 400 g

Magnesium stearate 500 g

Colloidal silicum dioxide 64 g and the whole is thoroughly mixed and compressed into tablets.

Formulation 9:

Capsules are prepared from the following mixture: 1-(2,6-dimethylρhenyl)-3- methylamidinourea hyrochloride 15 g Magnesium stearate 3 g

Finely divided silica sold under the trademark CAB-O-SIL by Godfrey L. Cabot, Inc., Boston, MA 2 g

Lactose 369 g

The mixture is filled into gelatin capsules, each capsule containing 500 mg of the mixture and thus 15 mg of 1-(2,6-dimethylphenyl)-3-methylamidinourea hydrochloride.

By analogous procedures, other amidinoureas of general Formula I above can be formulated in a similar manner for either oral or parenteral administration as injectable or infusible solutions. The solid or liquid formulations can also be dispersed in the food or dissolved in the drinking water or the liquid diet of the patient.

Claims

WE CLAIM:

1. In a process for the preparation of a compound of Formula I

comprising the reaction of an isocyanate of Formula II

with a guanidine of Formula III

with aqueous base, wherein:

R₁, R₂ and R₃ are each independently hydrogen, alkyl, cycloalkyl or aralkyl; or R₂ and R₃ together with the nitrogen atom to which they are attached form a 5, 6, or 7 membered ring which may include 0-2 additional heteroatoms of N, O or S; provided that at least one of R₁, R₂ or R₃ is other than hydrogen; the improvement comprising the use of a ketone as the reaction medium.

2. In a process according to Claim 1, the improvement comprising the use of acetone as the reaction medium.

3. In a process according to Claim 2, the improvement comprising removing the reaction product of Formula I from the reaction mixture by filtration.

4. In a process according to Claim 3, wherein the filtered reaction product is 1-(2,62dimethylphenyl)-3-methyl amidinourea.

5. A process for the preparation of a compound of Formula V

wherein a compound of Formula VI is added to a reaction solution prepared by mixing a compound of Formula VII

and a neutralizing quantity of aqueous base in a ketone solvent; wherein X and Y are hydrogen, alkyl, halo, alkoxy, haloalkyl or haloalkoxy; and R₂ and R₃ are hydrogen, alkyl, cycloalkyl, aralkyl or alkoxy; provided that at least one of R₂ and R₃ is other than hydrogen.

6. The process according to Claim 5 wherein the compound of Formula I is 1-(2 ,6-dimethylphenyl)-3-methylamidinourea.

7. A method for the preparation of a liquid pharmaceutical composition suitable for oral administration or parenteral injection, said composition comprising a pharmaceutically acceptable liquid vehicle and from 1 to 25 mg of a compound of the Formula I

R₁, R₂ and R₃ are each independently hydrogen, alkyl, cycloalkyl or aralkyl; or R₂ and R₃ together with the nitrogen atom to which they are attached form a 5, 6, or 7 membered ring which may include 0-2 additional heteroatoms of N, O or S; provided that at least one of R₁, R₂ or R₃ is other than hydrogen; which method comprises:

(a) dissolving an effective anti-diarrheal dosage amount of a salt of said compound in a liquid vehicle comprising either sterile water or a sterile electrolyte replenisher solution;

(b) sterilizing the solution by means of microfiltration;

(c) freeze-drying the sterilized solution to form a dessicated composition; and