NO880083L - PROCEDURE FOR THE PREPARATION OF AMORFE BENZIMIDAZOLD DERIVATIVES WITH IMPROVED SOLUBILITY AND ANTHELMINTIC ACTIVITY. - Google Patents

Description

This invention relates to amorphous benzimidazole derivatives

which exhibits increased solubility and anthelmintic activity.

The invention likewise relates to a preparation containing an amorphous benzimidazole derivative and a stabilizing amount of a stabilizing polymer.

The invention further relates to a method for producing the compounds and preparations according to the invention, a method for stabilizing amorphous benzimidazole derivatives,

a method of treating humans and animals for helminthiasis and/or fascioliasis and pharmaceutical preparations and veterinary preparations for such treatment.

Benzimidazole derivatives with anthelmintic activity

has long been known in the field, see e.g. US Patent Nos. 3,017,415, 3,480,642, 3,574,845, 3,657,267, 3,915,986, 3,929,821 and 3,993,682. However, conventional benzimidazole derivatives are rarely soluble to the desired extent in pharmaceutically acceptable carriers. Most conventional benzimidazole derivatives are almost insoluble in water. This causes problems both in the preparation of preparations and for biological availability.

It has long been assumed - since helminths (intestinal worms) settle in the digestive tract of patients and animals to be treated - that the benzimidazole derivatives administered as anthelmintic agents do not penetrate the blood stream to any significant extent. The biological availability of benzimidazole derivatives is typically very low. The plasma uptake of administered benzimidazole derivatives

to monogastric animals, is usually from 2% to 40% or less of the administered dose. The crystalline compound mebendazole is only absorbed in an amount of 3-4% when administered to humans. Thus, doses of crystalline mebendazole as large as 1 g t.i.d. are required.

to treat conditions such as alveolar echinococcosis.

It has now been shown that the plasma concentration of a benzimidazole derivative is of the greatest importance for it to work effectively, and that an increased concentration in the plasma correlates with increased activity. Other researchers have increased the uptake of benzimidazole derivatives in plasma by wet grinding the powders to increase the surface area, see e.g. European patent application no.

147 676-A. As a result, the concentration of a benzimidazole in the plasma may initially be high, but it will quickly decrease to the level achieved with unground, crystalline powders.

It has now been shown that the solubility can be increased

and the effectiveness of benzimidazole derivatives in that they are prepared in amorphous, non-crystalline form. The increased solubility results in a relatively constant plasma concentration of the benzimidazole derivatives at a level that is much higher than that which can be achieved through an increase in the surface area, which makes it possible to reduce the dose and/or to increase the effect. This, in turn, makes it possible to treat strains of intestinal worms that are resistant to anthelmintic benzimidazole derivatives in the doses that are currently administered. It has also been shown that one can stabilize the amorphous form (ie prevent the transfer of amorphous benzimidazole derivatives to crystalline benzimidazole derivatives) by forming a homogeneous mixture of an amorphous benzimidazole derivative and a stabilizing polymer. Such mixtures may be either solid (eg powders or moist cakes) or liquid. Amorphous preparations according to the invention are effective in doses of from 60 to 10% of the effective dose of a crystalline benzimidazole derivative.

The designations and expressions used in this description and the subsequent claims have the meanings given below, unless otherwise specifically stated.

With the expression "amorphous" is meant "mainly free of crystalline material", with the expression "mainly" meaning that between 70% and 100% of the sample is amorphous, preferably that between 80% and 100% of the sample is amorphous and more preferably that between 90% and 100% of the sample is amorphous. Amorphous benzimidazole dex-ivates can be separated from crystalline forms by several methods, including differential scanning calorimetry, X-ray diffraction, microscopic examination and solubility comparison. For example, using differential scanning calorimetry, amorphous oxfendazole can be distinguished from crystalline oxfendazole, because amorphous oxfendazole exhibits an exotherm at the melting point, while crystalline oxfendazole exhibits an endotherm. X-ray diffractograms of crystalline oxfendazole characteristically show large peaks between 5° and 25° (when plotting the intensity against 2&),

while X-ray diffractograms of amorphous oxfendazole show little, if any, peaks. Under microscopic examination using polarized light, crystalline oxfendazole exhibits birefringence, while amorphous oxfendazole does not. Using a Hanson dissolution apparatus with a buffer that gives pH 5.5, it can be shown that amorphous oxfendazole is between 2 and 20 times more soluble than crystalline oxfendazole. The amount of crystalline material in a sample of a benzimidazole derivative is measured using methods known in the art, e.g. by X-ray diffraction. Thus, an X-ray diffractogram of an amorphous material will show few peaks, if any at all, between 10° and 20° (2(5). If the area of any peaks between 10° and 20° is less than 10% of the area under baseline in an X-ray diffractogram of an amorphous material, the sample will contain less than 10% crystalline material.

With the expression "rapid precipitation" is meant precipitation of

a solid from a solution at a rate sufficient to avoid crystallization. By "rapid addition" is meant the addition of a solution or of a reagent at high speed. Usually, the addition is rapid if the solution or reagent is added within up to 10 minutes, preferably within up to one minute.

The term "anthelmintic" refers to compounds useful in the treatment of helminthiasis in animals.

The term "benzimidazole derivative" refers to compounds of formula 1:

or a pharmaceutically acceptable salt thereof, wherein

R is lower alkyl; and

R., is -S(0) R,. , -OR- or

1 m 2 2

Y. ( CH_, ) Y_R0 where

1 2'n 2 3

Yl°^^2uavnen9i9of each other is 0, S or S(O), R^ is lower alkyl, phenyl or naphthyl, and

n is 1, 2, 3 or 4;

R 2 is lower alkyl, cycloalkyl, alkenyl with from

3 to 7 carbon atoms, alkynyl of from 3 to 7 carbon atoms, phenyl, benzyl, phenylethyl or naphthyl; and

m is 0 or 1.

The term "oxfendazole" refers to the compound methyl-5-(phenylsulfinyl)-1H-benzimidazol-2-yl-carbamate, which is also known under the name 5-phenylsulfinyl-2-carbomethoxyaminobenzimidazole.

The term "fenbendazole" refers to the compound methyl-5-(phenylthio)-1H-benzimidazol-2-yl-carbamate, which is also known under the name 5-phenylthio-2-carbomethoxy-aminobenzimidazole.

The term "RS-8852" refers to the compound methyl-5-(n-propylsulfinyl)-1H-benzimidazol-2-yl-carbamate,

which is also known under the name 5-n-propylsulfinyl-2-carboxymethoxyaminobenzimidazole.

The term "albendazole" refers to the compound methyl-5-(n-propylthio)-1H-benzimidazol-2-yl-carbamate, which is also known under the term 5-n-propylthio-2-carbomethoxy-aminobenzimidazole.

The term "oxibendazole" refers to the compound methyl-5-(propoxy)-1H benzimidazol-2-yl-carbamate, which is also known under the term '5-propoxy-2-carboxymethoxy-aminobenzimidazole.

The term "animal" is intended to include humans as well.

The term "pharmaceutical preparation" refers to preparations for the treatment of humans or domestic animals, including (but not limited to) cattle, swine, dogs and sheep.

The term "veterinary preparation" refers to preparations for the treatment of domestic animals, including cattle, horses, pigs, dogs, sheep and the like (but not limited thereto).

The term "pharmaceutically acceptable salt" refers to salts of the compounds in question which exhibit the desired pharmacological activity, and which are neither biologically undesirable nor undesirable in any other way. These salts are formed with inorganic acids, such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid or phosphoric acid, or with organic acids, such as acetic acid, propionic acid, glycolic acid, pyrotartaric acid, malonic acid, succinic acid, malic acid, maleic acid, fumaric acid, tartaric acid, citric acid, benzoic acid, cinnamic acid, mandelic acid, methanesulfonic acid, ethanesulfonic acid, p-toluenesulfonic acid and the like. The term "pharmaceutically acceptable" includes all salts acceptable in human or veterinary medicine.

The term "effective amount" refers to the amount of benzimidazole derivative of formula 1 necessary to treat an animal to be treated. The effective amount of an amorphous compound will vary from compound to compound. Generally, an effective amount of an amorphous compound of formula 1 will be between 60% and 10% of the effective amount of the compound in a crystalline form.

An effective amount for anthelmintic use of compounds of formula 1 will usually be in the range of 0.02 mg/kg to 20 mg/kg. An effective amount of amorphous oxfendazole for cattle will usually be from 1 mg/kg to 4 mg/kg, preferably between 2 mg/kg and 3 mg/kg and more preferably about 2.8 mg/kg. An effective amount of amorphous oxfendazole for sheep is usually between 1 mg/kg and 4 mg/kg, preferably between 2 and 3.5 mg/kg, more preferably about 3 mg/kg. An effective amount of amorphous oxfendazole for pigs is usually between 2 mg/kg and 8 mg/kg, preferably between 3 mg/kg and 5 mg/kg, more preferably about 4 mg/kg. An effective amount of amorphous oxfendazole for dogs is usually approx. 3 mg/kg.

The term "stabilizing polymer" refers to derivatives of compounds capable of preventing or inhibiting crystallization of benzimidazole derivatives. Stabilizing polymers include (but are not limited to) cellulose derivatives, polyvinylpyrrolidone and derivatives thereof, xanthan gums, pectins, alginates, gum tragacanth and tragacanth gum derivatives, gum arabic and derivatives thereof, carrageenans, agar and derivatives, polysaccharides from microbial sources, arabinogalactans, galactomannans, dextrans and the like. Preferred stabilizing polymers are non-toxic to the animal to be treated, in the amounts in which they are to be administered. Preferred stabilizing polymers are cellulose derivatives and xanthan gums. More preferred stabilizers are cellulose derivatives.

The term "cellulose derivative" refers to derivatives of cellulose which are capable of preventing or inhibiting the crystallization of benzimidazole derivatives. Preferred cellulose derivatives are non-toxic to the animal to be treated, in the amounts in which they are to be administered. The cellulose derivatives include (but are not limited to) methylcellulose, sodium carboxymethylcellulose, hydroxypropylmethylcellulose. hydroxypropylcellulose and the like. Preferred cellulose derivatives are methylcellulose and sodium carboxymethylcellulose, especially methylcellulose. Most Fore-(R) (5)

drawn are Methocel ^ A4C Premium, Methocel w A-15Premium (supplied from Dow Chemical - USA) and sodium carboxymethylcellulose ("CMC 7MFk", supplied by Hercules, Inc., Wilmington, Delaware).

The terms "stable amorphous mixture" and "stable amorphous preparation" refer to mixtures, respectively preparations containing an amorphous compound of formula 1 and a stabilizing amount of a stabilizing polymer.

A "stabilizing amount" of a stabilizing polymer is the amount necessary to prevent an amorphous compound of formula 1 from converting to a crystalline form. The stabilizing amount varies depending on the compound and the stabilizing polymer, but is between 0.0001 g per g compound and 0.9 g per g compound, preferably between 0.001 and 0.15 g per g compound, more preferably between 0.002 and 0.05 g per g connection and preferably approx. 0.03 g per g connection. It should be noted that the maximum amount of stabilizing polymer in the finished pharmaceutical preparation or veterinary preparation is determined only by economic factors or by need. In practice, the maximum amount of stabilizing polymer will be the maximum amount that can be administered to the patient without harming him. Typical ratios of the stabilizing polymer to the compound of formula 1 required to achieve stabilization of the compound of formula 1 (with percentages indicated in parentheses) include the values 0.001/1 (0.1%); 0.1/1 (10%); and 0.3/1 (30%) .

The name Keltrol ^ refers to a xanthan gum which is commonly used in the pharmaceutical industry as a thickening agent. Keltrol^ Cr) is formed by fermentation of Xanthomonas compestris and is supplied by Kelco Co.,

San Diego, California. The production of xanthan gums is described in US Patent Nos. 3,433,708 and 3,557,016.

The term "Carbopol" refers to an acrylic acid polymer resin with an average equivalent weight of approx. 76. "Carbopol" is widely used in the pharmaceutical industry as a suspending agent and is available on the market.

The term "Masonex" refers to a hemicellulose extract obtained as a by-product in a process for the production of masonite sheets. Masonex is a viscous, dark colored syrup that is commonly used in the pharmaceutical industry as a drug carrier, and is available commercially.

The term "treatment" as used herein covers any treatment of a disease in a mammal and includes: (i) inhibition of the disease, i.e. inhibition of its development, and (ii) alleviation of the disease, i.e. bringing about a regression of the disease.

The term "crumble" refers to a granulated mixture containing an active ingredient, corn syrup and regular feed, which is pelletized and crushed to form particles less than 5 mm in diameter.

The term "alkyl" refers to a saturated hydrocarbon radical containing 1-20 carbon atoms. "Lower alkyl" refers to an alkyl radical of 1-6 carbon atoms, e.g. methyl, ethyl, n-propyl, i-propyl, butyl, s-butyl, pentyl and hexyl.

The term "cycloalkyl" refers to a cyclic, saturated hydrocarbon radical containing 3-8 carbon atoms, e.g. cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl.

The term "alkenyl" refers to a hydrocarbon radical with 3-7 carbon atoms, containing a double bond, e.g. propenyl, allyl, butenyl, pentenyl, hexenyl and heptenyl.

The term "alkynyl" refers to a hydrocarbon radical with 3-7 carbon atoms, containing a triple bond, e.g. propynyl, propargyl, butynyl, pentynyl, hexynyl and heptynyl.

The term "Alkoxy" refers to a radical

of the form RO-, where R is lower alkyl or cycloalkyl as defined above.

The term "halogen" refers to fluorine, chlorine, bromine or iodine.

According to one aspect of the invention, there is provided a benzimidazole derivative of formula 1 or a pharmaceutically acceptable salt thereof in an amorphous (non-crystalline) form:

or a pharmaceutically acceptable salt thereof, wherein R is lower alkyl; and R^ is -S(0)mR2, ~0R2e-'--'-er ()n^2^3' where ^ 1°9Y2 independently of each other is 0, S or S(0), R^ is lower alkyl , phenyl or naphthyl; and

n is 1, 2, 3 or 4; R 2 is lower alkyl, cycloalkyl, alkenyl of from 3 to 7 carbon atoms, alkynyl of from 3 to 7 carbon atoms, phenyl, benzyl, phenylethyl or naphthyl; and m is 0 or 1.

According to another aspect of the invention, a stable, amorphous preparation comprising a stabilizing amount of a stabilizing polymer and an amorphous compound of formula 1 is provided.

According to a further aspect of the invention, a method for the production of amorphous benzimidazole derivatives is provided, according to which a benzimidazole derivative of formula 1 is precipitated from an acidic or basic solution by rapid addition of a sufficient amount of base or acid to set the solution's pH value of the lowest benzimidazole solubility.

According to yet another aspect of the invention, a method for stabilizing stable amorphous preparations is provided, according to which a benzimidazole derivative of formula 1 is rapidly precipitated from an acidic or basic solution by adding a basic or acidic solution containing a stabilizing amount of a stabilizing polymer.

According to yet another aspect of the invention, a method for stabilizing stable amorphous preparations is provided, according to which a benzimidazole derivative of formula 1 or a combination of benzimidazole derivatives of formula 1 is spray-dried from an acidic or basic solution containing a stabilizing amount of a stabilizing polymer.

According to a further aspect of the invention, a pharmaceutical preparation or veterinary preparation is provided, which preparation comprises a stabilizing amount of a stabilizing polymer and an amorphous compound of formula 1 or a combination of amorphous compounds of formula 1.

According to a further aspect of the invention, there is provided a method of treating an animal for helminthiasis, which method comprises administering to a mammal in need of such treatment an effective amount of an amorphous compound of formula 1 or a combination of amorphous compounds of formula 1.

The invention also relates to the use of an amorphous compound of formula 1 or a combination of amorphous compounds of formula 1 for the production of a veterinary preparation for the treatment of helminthiasis.

According to another aspect of the invention, a method for the preparation of an amorphous compound of formula 1 is provided:

or a pharmaceutically acceptable salt thereof, wherein

R is lower alkyl; and

R1 is -S(0)mR2, -0R2 or Y;[ (CH2 )nY2R3 , where

Y 1 and Y 2 are independently 0, S or S(O), R 2 is lower alkyl, phenyl or naphthyl, and n is 1, 2, 3 or 4;

f*2 is lower alkyl, cycloalkyl, alkenyl with from

3 to 7 carbon atoms, alkynyl of from 3 to 7 carbon atoms, phenyl, benzyl, phenylethyl or naphthyl; and

m is 0 or 1,

according to which one:

A. (a) dissolves a compound of formula 1 in a base or acid to dissolve or solubilize the compound of formula 1 and then (b) adds an amount of an acid or base under such conditions that the compound of formula 1 precipitates amorphous form, or B. (a) dissolves a compound of formula 1 in an acid or base to dissolve or solubilize the compound of formula 1, and then (b) spray-dry the solution from step (a) to form an amorphous compound of formula 1 , or C. (a) dissolves a compound of formula 1 in an acid or base solution containing a stabilizing amount of a stabilizing polymer and then (b) spray dries the solution from step (a) to form an amorphous compound of formula 1, or D. (a) dissolves a compound of formula 1 in an acid or base in a first pH range to dissolve or solubilize the compound of formula 1 and then (b) adds a stabilizing amount of a stabilizing polymer in a solution with a second pH range opposite to that used in step (a), and then (c) adding acid or base to restore a third acidic or basic pH range on the same side of the pH scale as the first pH range to form an amorphous form of a compound of formula 1.

According to the first aspect of the invention, there is provided a non-crystalline, amorphous compound of formula 1:

or a pharmaceutically acceptable salt thereof, wherein

R is lower alkyl; and

R, is -S(0) R_, -0Ro or Y^CH-) Y0R0, where

1 m2 2 1 2 n 2 3

Y₂ and Y₂ are independently 0, S or S(O), R₂ is lower alkyl, phenyl or naphthyl, and

n is 1, 2, 3 or 4;

R 2 is lower alkyl, cycloalkyl, alkenyl with from

3 to 7 carbon atoms, alkynyl of from 3 to 7 carbon atoms, phenyl, benzyl, phenylethyl or naphthyl; and

m is 0 or 1.

A preferred type of compounds according to the invention are the amorphous benzimidazole derivatives of formula 1, where R 1

is -S(0)mR 2 and R is methyl, especially where m is 1. Preferred compounds are those where R 2 is ethyl, n-propyl, 2-butyl or phenyl, especially n-propyl or phenyl. Another preferred class is that wherein R 1 is -S(O) R 2 , where m is 1 and R is methyl. Preferred compounds are those where R 2 is n-propyl or phenyl. Another preferred class is that wherein R 1 is 0 R 2 and R 2 is methyl. Preferred compounds are those where R 2 is n-propyl or phenyl. Another preferred class is that where R^ is - Y^(CH2)nY2R3 and R is metnv1'especially where Y^ is S(0) and Y2 is 0. Preferred compounds are those where R^ is methyl, especially where n is 1 or 2.

According to another aspect of the invention, a preparation comprising a compound of formula 1 and a stabilizing amount of a stabilizing polymer is provided. A preferred species is that in which said stabilizing polymer is a cellulose derivative. A more preferred species is that in which said cellulose derivative is methylcellulose. A preferred class is that where R 1 is -S(O)m R 2 and R is methyl, especially where m is 1. Preferred compounds are those where R is ethyl, n-propyl, 2-butyl or phenyl, especially n-propyl or phenyl. Another preferred class is that in which R1 , is -S(0) m R2„

where m is 0 and R is methyl. Preferred compounds are those where R 1 is n-propyl or phenyl. Another preferred class is that wherein R^ is OR^ and R is methyl. Preferred compounds are those where R 1 is n-propyl or phenyl. Another preferred class is that wherein R^ is ~Yi(CH2)nY2R3 and R is methyl, especially where Y^ is S(0) and Y^ is 0. Preferred compounds are those where R^ is methyl, especially where n is 1 or 2.

According to another aspect of the invention, a method for the production of amorphous benzimidazole derivatives is provided, according to which a compound of formula 1 is rapidly precipitated from an acidic or basic solution with a first pH value by adjusting the solution's pH value at a second pH value at which the compound of formula 1 has lower solubility. According to a preferred embodiment of the method, the second pH value is approximately the pH value which gives the least solubility of the selected crystalline benzimidazole derivative (usually 4-6), especially when the first pH value is between 8 and 11. This embodiment is particularly advantageous when the compound with formula 1 is first formed or dissolved in a solution with a pH value lower than 4 (especially when the solution is acetic acid, propionic acid, hydrochloric acid, phosphoric acid, formic acid or nitric acid, preferably using concentrated formic acid or hydrochloric acid, more preferably formic acid), and base is then added to increase the pH value to approx. 8 (especially when the base is an organic or inorganic base, such as ammonium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, sodium methylate, sodium ethylate, sodium hydride, triethylamine or pyridine, it being preferable to use ammonium hydroxide or sodium hydroxide in aqueous or methanolic solution, especially ammonium hydroxide or sodium hydroxide in aqueous solution), after which a second acid is added to lower the pH to approx. 5 (preferably the second acid is the same acid as the first acid, and in particular the second acid is concentrated formic acid). The above embodiment of the method is likewise particularly advantageous when the compound of formula 1 is first formed or dissolved in a solution with a pH value higher than 7.5 (preferably the solution is an aqueous or methanolic solution of an organic or inorganic base such as ammonium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, sodium methylate, sodium ethylate, sodium hydride, triethylamine or pyridine, preferably using ammonium hydroxide or sodium hydroxide in aqueous or methanolic solution, especially ammonium hydroxide or sodium hydroxide in aqueous solution), after which a concentrated acid is added to lower the pH value to approx. 5 (in particular the acid is acetic acid, propionic acid, hydrochloric acid, phosphoric acid, formic acid or nitric acid, and preferably concentrated formic acid or hydrochloric acid is used, most preferably concentrated formic acid.

According to a further aspect of the invention, a method for the preparation of amorphous benzimidazole derivatives is provided, according to which a compound of formula 1 is spray-dried from a solution, in particular an acidic solution. According to a preferred embodiment of the method, an acidic solution is used consisting of acetic acid, propionic acid, hydrochloric acid, phosphoric acid, formic acid or nitric acid, preferably concentrated formic acid or hydrochloric acid, more preferably concentrated formic acid and a compound of formula 1.

According to another aspect of the invention, a method for the production of stable amorphous benzimidazole preparations is provided, according to which a compound of formula 1 and a stabilizing amount of a stabilizing polymer are rapidly precipitated from an acidic or basic solution with a first pH value by setting the solution's pH value to a second pH value at which the compound with formula 1 has a lower solubility. According to a preferred embodiment of the method, the second pH value is approximately equal. the pH value that gives the smallest solubility for the selected crystalline benzimidazole derivative (between 4 and 6), especially when the first pH value is between 8 and 11. This embodiment is particularly advantageous when the compound of formula 1 is first formed or dissolved in a solution with a pH value lower than 4 (especially when the solution is concentrated formic or hydrochloric acid, especially formic acid), after which base and a stabilizing amount of a stabilizing polymer are added to raise the pH to about 8 (especially when the base is aqueous or methanolic ammonium hydroxide or sodium hydroxide, preferably aqueous ammonium hydroxide or sodium hydroxide), after which a second acid is added to lower the pH to about 5 (especially when the second acid is hydrochloric acid or concentrated formic acid, preferably concentrated formic acid). The aforementioned preferred embodiment is also particularly advantageous when the compound of formula 1 is first formed or dissolved in a solution with a pH higher than 7.5 containing a stabilizing amount of a cellulose derivative (especially when the solution is aqueous or methanolic ammonium hydroxide or sodium hydroxide, preferably aqueous ammonium hydroxide or sodium hydroxide), after which an acid is added to lower the pH value to approx. 5 (especially when the acid is concentrated formic acid).

According to another aspect of the invention, a method for the production of stable amorphous benzimidazole preparations is provided, according to which a compound of formula 1 and a stabilizing amount of a stabilizing polymer are spray-dried from a solution, especially an acidic or basic solution, especially an acidic solution.

According to a preferred embodiment of this method, a solution comprising concentrated formic acid, a stabilizing amount of a stabilizing polymer and a compound of formula 1 is used.

According to a further aspect of the invention, a method for stabilizing benzimidazole derivatives or combinations of benzimidazole derivatives in an amorphous form is provided, according to which a compound of formula 1, or a combination of compounds of formula 1, is rapidly precipitated from an acidic or basic solution by adding a basic or acidic solution containing a stabilizing amount of a stabilizing polymer.

According to a further aspect of the invention, there is provided a method of treating an animal for helminthiasis, according to which one administers to a mammal in need of such treatment an effective amount of a composition comprising a stabilizing amount of a stabilizing polymer and an amorphous compound of formula 1, or a combination of amorphous compounds of formula 1.

According to another aspect of the invention, a pharmaceutical preparation or a veterinary preparation for the treatment of helminthiasis is provided, which preparation comprises a stabilizing amount of a stabilizing polymer and an amorphous compound of formula 1, or a combination of amorphous compounds of formula 1.

The invention likewise relates to the use of an amorphous compound of formula 1 for the production of a veterinary preparation for the treatment of helminthiasis.

The preparations according to the invention show increased solubility and effectiveness compared to the preparations containing crystalline benzimidazole derivatives.

The preparations according to the invention can be tested for direct potency (where experimental animals are infected, given the preparation according to the invention or a neutral solvent and then autopsied for the detection of remaining parasites) or tested with regard to the blood plasma level in cases where the preparation contains individual compounds with known effectiveness.

solvent in which the compound does not dissolve, or, preferably, by one of the following methods.

According to a first method, a compound of formula

1 dissolved or prepared in an acidic solution with a pH value lower than 3. Currently preferred solvents are concentrated HCl and concentrated formic acid; concentrated formic acid is most preferred. The amorphous compound of formula 1

can precipitate directly from the resulting acidic solution by rapid addition of base with stirring. However, due to the solubility properties of the compounds involved, it is preferable to first make the solution basic to a pH of approx. 8, as it is ensured that no precipitation is initiated. The acidic solution can be made basic with any strong base (see above list), e.g. sodium hydroxide in water or alcohol (such as methanol), preferably sodium hydroxide in water. The resulting basic solution is then acidified until the pH of the solution has become approximately equal to the pH value which gives the least benzimidazole solubility, which means a pH value of 4-6. The basic solution can be acidified with any concentrated acid (see above list), preferably with concentrated formic acid. The resulting solution is then stirred until the amorphous compound of formula 1 aggregates and precipitates, whereupon it is collected, washed and dried. For example, 10 g of crystalline oxfendazole are dissolved in 20 ml of concentrated (95-97%) formic acid. A solution of 30 g of NaOH in 5 1 of water is then added slowly, e.g. with a speed of approx. 60 ml/min, while stirring with high shear forces, care being taken to avoid the incorporation of air or precipitation occurring. Then add approx. 17 ml of concentrated formic acid with stirring, until the pH value of the resulting solution becomes 4-5. The solution is stirred until the amorphous oxfendazole precipitates. The precipitate is collected by vacuum filtration, washed with distilled water and dried, whereby amorphous oxfendazole is obtained.

According to a second method, a compound becomes

Admin's tree ring

Anthelmintic preparations of a compound of formula

1 are effective when administered to a patient's digestive system, e.g. orally or intraruminally. When the animal to be treated is a ruminant, it is preferred to administer the new preparations intraruminally.

Generally, a therapeutically effective amount for amorphous oxfendazole will range from 0.02 to 20 mg/kg body weight. Other amorphous, anthelmintic benzimidazole derivatives may have deviating dosage ranges. Oxfendazole is preferably administered intraruminally to cattle in doses of between 1.5 mg/kg and 3 mg/kg, preferably in a dose of 2.8 mg/kg body weight.

For an animal weighing 100 kg, in other words, a therapeutically effective amount of amorphous fenbendazole will preferably be from 2 to 2000 mg of amorphous oxfendazole, preferably between 150 and 300 mg, preferably approx. 280 mg.

Preferably, amorphous oxfendazole is administered orally

to sheep in doses of between 2 mg/kg and 3.5 mg/kg, preferably in a dose of 3 mg/kg body weight. For an animal weighing 30

kg, in other words, a therapeutically effective amount of amorphous oxfendazole will preferably be from 60 mg to 105 mg, preferably approx. 90 mg.

Forward tilling

Oxfendazole and similar benzimidazole derivatives are available

in the trade. Oxfendazole and similar benzimidazole derivatives can alternatively be prepared according to the method described in US patent document no. 3 929 821,

Stabilizing polymers are available commercially. For example, methylcellulose is sold by Dow Chemical under the brand name Metho-® (R)

cel A-15 and Methocel ^ A4C. Hydroxypropylcellulose is sold by Dow Chemical under the trade name Methocel^E-15 or Methocel^-S. Sodium carboxymethyl cellulose is sold by Hercules, Inc. under the trade name "CMC 7MF".

Amorphous compounds of formula 1 can be prepared by

a number of methods which are characterized by the fact that the compound with formula 1 precipitates out quickly and is not given time to reach equilibrium and crystallize. In the following methods, "dried" shall be interpreted as either dried to a solid or dried to a moist cake. For example, a compound with formula 1 can be precipitated from a solution by adding a

with formula 1 first dissolved in a basic, aqueous or alcoholic solution. The base can be any strong base, such as sodium hydroxide, ammonium hydroxide, potassium hydroxide and the like. The resulting basic solution is then acidified until the solution's pH value has become approximately equal to the pH value that gives the least benzimidazole solubility, i.e. a pH value of 4-5. The basic solution can be acidified with any concentrated acid, concentrated formic acid being preferably used. The resulting solution is then stirred until amorphous compound of formula 1 precipitates, whereupon the precipitate is collected, washed and dried. For example, 10 g of crystalline oxfendazole is dissolved in a solution of 30 g of NaOH in 5 liters of water. Concentrated formic acid is then added while stirring until the pH value of the resulting solution becomes 4-5. The solution is stirred until amorphous oxfendazole precipitates. The precipitate is collected by vacuum filtration, washed with distilled water and dried, whereby amorphous oxfendazole is obtained.

According to a third method, a compound becomes

1 dissolved or prepared in an acidic solution with a pH lower than 3. Currently preferred solvents are concentrated HCl and formic acid; most preferred is concentrated formic acid

is. The solution is then spray-dried to form an amorphous compound according to the invention. For example, 10 becomes

g of crystalline oxfendazole dissolved in 20 ml of concentrated (95-97%) formic acid and the solution spray-dried, whereby amorphous oxfendazole is obtained.

Stable amorphous preparations according to the invention can be prepared by any of the following methods.

According to a first method, a compound becomes

of formula 1 dissolved or prepared in an acidic solution with a pH less than 3. Currently preferred solvents are concentrated hydrochloric acid, phosphoric acid, propionic acid, acetic acid and formic acid. Most preferred is concentrated formic acid. The amorphous compound of formula 1 can be precipitated directly from the resulting acidic solution by rapid addition of

base while stirring. However, due to the solubility properties of the compounds involved, it is preferred

that you first alkalize the solution to a pH value of

about. 8 using a solution containing a stabilizing amount of a stabilizing polymer such as a cellulose derivative, ensuring that no precipitation is initiated. The acidic solution can be made alkaline with any base, e.g. with ammonium hydroxide or sodium hydroxide in water or alcohol (such as methanol), preferably with ammonium hydroxide or sodium hydroxide in water. The stabilizing polymer is preferably a cellulose derivative, preferably methylcellulose or sodium carboxymethylcellulose, especially methylcellulose. The resulting basic solution is then acidified until the pH value of the solution is approximately equal to the pH value which gives the least benzimidazole solubility, namely a pH value of 4-5. The basic solution can be acidified with any concentrated acid. Concentrated formic acid is preferred. The resulting solution is then stirred until the amorphous preparation precipitates and aggregates, after which the precipitate is collected, washed and dried. For example, 10 g of crystalline oxfendazole are dissolved in 20 ml of concentrated (95-97%) formic acid. A solution of 30 g of NaOH and 0.02 g of methylcellulose in 5 ml of water is then slowly added (e.g. at a rate of about 60 ml/min) with stirring using high shear forces, taking care to avoid incorporation of air. Then add approx. 17 ml of concentrated formic acid with stirring, until the pH value of the resulting solution becomes 4-5. The solution is stirred until the stabilized, amorphous oxfendazole precipitates. The precipitate is collected by vacuum filtration, washed with distilled water and dried, whereby the stable, amorphous preparation is obtained.

According to a second method, a compound becomes

with formula 1 first dissolved in a basic, aqueous or alcoholic solution containing a stabilizing amount of a stabilizing polymer. The base can be any strong base, such as ammonium hydroxide, sodium hydroxide,

potassium hydroxide or the like. The stabilizing polymer is preferably a cellulose derivative, more preferably methylcellulose or sodium carboxymethylcellulose, especially methylcellulose. The resulting basic solution is then acidified until the pH value of the solution has become approximately equal to the pH value that gives the least benzimidazole solubility, which is a pH value of 4-5. The basic solution can be acidified with any concentrated acid, preferably with concentrated formic acid. The resulting solution is then stirred until the stabilized, amorphous preparation precipitates, after which the precipitate is collected, washed and dried. For example, dissolve 10 g of crystalline oxfendazole and 0.02

(R)

g Methocel ^ A4C in a solution of 30 g NaOH in 5 1 water.

Concentrated formic acid is then added while stirring until the pH value of the resulting solution becomes 4-5. The solution is stirred until the amorphous preparation falls out. The precipitate is collected by vacuum filtration, washed with distilled water and dried, whereby stabilized, amorphous oxfendazole is obtained.

According to a third method, a stabilizing amount of a stabilizing polymer and a compound of formula 1 is dissolved or prepared in an acidic solution with a pH lower than 3. Currently, a preferred solvent is concentrated hydrochloric acid and formic acid. It is preferred to use concentrated formic acid. The solution is then spray-dried to form the new stabilized, amorphous preparation. Example(s)

example, 10 g of crystalline oxfendazole and 0.02 g of Methocel A-15 are dissolved in 20 ml of concentrated (95-97%) formic acid and the solution spray-dried to form the stabilized amorphous oxfendazole.

The methods described above can also be used using mixtures of compounds of formula 1. These methods can be carried out at ambient temperature and pressure.

The following examples illustrate the invention.

Example 1

(A) 10 g of crystalline oxfendazole is dissolved in 20 ml of 95-97% formic acid. A solution of 30 g NaOH in 5 1 distilled

water is then slowly added to the oxfendazole solution over approx. 90 minutes with stirring using high shear forces, care being taken to avoid the ingress of air and precipitation. Concentrated formic acid is then quickly added with stirring, until the pH value is between 4 and 5. The resulting solution is stirred until the amorphous oxfendazole has precipitated, after which it is collected by vacuum filtration, washed with distilled water and dried.

Samples of amorphous oxfendazole are prepared according to the method described above and finely ground. The diffractograms are obtained using a Nicolet Model 12 X-ray Diffractometer using CuK radiation, sweeping from 3°

^

to 30 20, with step width 0.05 and step time 2 seconds.

A test plate of 0.016 is used. The sample is placed on the plate and smoothed with a glass plate. The number of counts above the background noise is obtained by computer analysis. The total peak area between 10° and 20° 29 using amorphous oxfendazole is compared with the total peak area between 10° and 20° 20 obtained using crystalline oxfendazole. The peak area obtained with amorphous oxfendazole is less than 10% of the peak area obtained with crystalline oxfendazole.

(B) 10 g of crystalline RS-8852 is dissolved in 20 ml of 95-97% formic acid. A solution of 30 g of NaOH in 5 l of distilled water

then slowly added to the RS-8852 solution over 90 minutes with stirring using high shear forces, care being taken to avoid entrainment of air and precipitation. Concentrated formic acid is then rapidly added with stirring until the pH value is between 4 and 5. The resulting solution is stirred until the amorphous RS-8852 precipitates, after which the precipitate is collected by vacuum filtration, washed with distilled water and dried.

Samples of amorphous RS-8852 are prepared

according to the procedure described above and finely ground. The diffractograms are obtained using a Nicolet Model 12 X-ray Diffractometer using CuK^ radiation, sweeping from 3° to 30° 2$, with step width 0.05° and step time

2 seconds. A test plate of 0.016 is used. The sample is placed on the plate and smoothed with a glass plate. The number of counts above the background noise is obtained by computer analysis. The total peak area between 10° and 2 0° 2 0 using amorphous RS-8852 is compared with the total peak area between 10°

and 20 20 obtained using crystalline RS-8852. The peak area obtained with amorphous RS-8852 is less than 10% of the peak area obtained with crystalline RS-8852. (C) Similarly, by proceeding as indicated under points A or B above but using albendazole, oxibendazole, fenbendazole or another benzimidazole derivative instead of oxfendazole, the corresponding amorphous compounds are obtained, all of which show X-ray diffraction patterns with peak areas that are less than 10% of the peak area obtained for the crystalline compound.

Example 2

(A) 67.94 g of crystalline oxfendazole is dissolved in 95% formic acid. A solution of 203.9 g of sodium hydroxide in 33.30

liters of distilled water and 676 ml of 5% methylcellulose are then added slowly using high shear forces, care being taken to avoid the ingress of air or precipitation. Concentrated formic acid is then added with stirring until the pH is between 4 and 5. The resulting solution is stirred until amorphous oxfendazole has been formed, where it is collected by vacuum filtration, washed with distilled water (followed by resuspension in 1% -ig methylcellulose), centrifuged and dried. The peak area of the resulting amorphous oxfendazole with methylcellulose present showed less than 10% of the peak area of crystalline oxfendazole by the X-ray diffraction procedure of Example 1.

(B) 20 g of RS-8852 is dissolved in 20 ml of 95-97% formic acid. While stirring well, the formic acid solution is added slowly

1 liter of distilled water at 5°C containing 70 g of sodium hydroxide and 40 g of methylcellulose. While stirring, concentrated formic acid is added to the mixture until the pH value is between 4 and 5. Amorphous RS-8852 is formed, after which it is collected by centrifugation at 5°C. The mother liquor is decanted and amorphous RS-8852 is resuspended in 500 ml of 2% methylcellulose at 5°C. The solution is centrifuged again to recover amorphous RS-8852, which is washed and dried. The peak area of the resulting amorphous RS-8852

with methylcellulose present showed less than 10% of the peak area of crystalline RS-8852 by the X-ray diffraction procedure of Example 1. (C) Similarly, by proceeding as indicated under A or B above but using fenbendazole,

albendazole, oxibendazole or another benzimidazole derivative instead of RS-8852, the corresponding stabilized compounds are obtained which, by X-ray diffraction, show a peak area that is less than 10% of the peak area of the corresponding crystalline compound by the procedure according to example 1.

Example 3

(A) 10 g of oxfendazole is dissolved in 20 ml of concentrated (95-97%) formic acid. The resulting solution is then spray-dried using a conventional spray-drying apparatus, whereby an amorphous oxfendazole is obtained which, in the X-ray diffraction procedure according to example 1, gives a peak area which is less than 10% of the peak area obtained for crystalline oxfendazole . (B) In a similar manner, proceeding as indicated under point (A) above but using RS-8852, albendazole,

fenbendazole, oxibendazole or another benzimidazole derivative instead of oxfendazole, the corresponding spray-dried stabilized amorphous preparations are obtained which, in the X-ray diffraction procedure according to example 1, give a peak area that is less than 10% of the peak area obtained for the corresponding crystalline compound.

Example 4

(A) 10 g of oxfendazole and 0.02 g of Methocel ® A-15 are dissolved in concentrated (95-97%) formic acid. The resulting solution is then spray dried using a conventional spray dryer, whereby an amorphous oxfendazole is obtained which, with Methocel (R) A-15 present, exhibits a peak area which is less than 10% of the peak area of crystalline fenbendazole by the X-ray diffraction procedure according to Example 1. (B) In a similar way, proceeding as indicated under point A above but using RS-8852, albendazole, fenbendazole, oxibendazole or another benzimidazole derivative instead of oxfendazole, the corresponding spray-dried amorphous preparations are obtained with Methocel A-15 present, as in the X-ray diffraction procedure according to Example 1 shows a peak area which is less than 10% of the peak area of the corresponding crystalline compound.

Example 5

Injectable preparation

(A) A preparation suitable for injection was prepared

with the following composition:

The preparation was prepared in the following way: The polyethylene glycol was dissolved in a small amount of water at 70°C. The oxfendazole (with or without stabilizing polymer present), the methylparaben and the propylparaben were then added to this solution. The methyl cellulose was then dissolved in approx. 10 ml of water, and the resulting solution was stirred into the solution of amorphous oxfendazole, after which distilled water was added to the desired volume.

Example 6

Suspension preparations

(A) A preparation suitable for oral or intraruminal administration was prepared with the following composition:

The preparation was prepared as in example 5 above, in that the Keltrol ® component was added in solution together with the methylcellulose.

(B) Another preparation suitable for oral or intraruminal administration was prepared with the following composition:

The preparation (with or without the presence of stabilizing polymer) was prepared as in Example 5 above, with the Keltrol ® component and the Carbopol component being added in solution together with methylcellulose.

(C) Another preparation suitable for oral or intraruminal administration was prepared with the following composition:

The preparation (with or without stabilizing polymer present) was prepared as indicated under point B above.

Example 7

Preparations for sprinkling on animal manure

(A) A spreadable preparation suitable for sprinkling on animal feed was prepared with the following composition:

The preparation was prepared as follows: the powdered amorphous oxfendazole (with or without stabilizing polymer present), the methylcellulose and the lactose were mixed together and the mixture ground with corn syrup. After drying, the granules were compressed into tablets and the tablets crushed into particles with a diameter of less than 5 mm.

(B) Another preparation suitable for sprinkling on animal feed was prepared with the following composition:

The preparation was prepared as follows: the methylcellulose is dissolved in as little water as possible, and the amorphous oxfendazole (with or without stabilizing polymer present) is added. The resulting slurry is then mixed with the "Masonex" ingredient, and the mixture is mixed with the wheat bran.

The resulting mixture is then dried in a tray drying oven.

(C) A suspension preparation suitable for application as

a dressing on animal feed, was produced with the following composition:

The preparation was prepared according to the procedure described in example 6(A).

Example 8

Table11 preparations

(A) A tablet preparation suitable for administration to dogs and similar mammals was prepared with the following composition:

The preparation was prepared as follows: a paste is prepared using 7.5 mg of starch, the methylcellulose and the smallest possible amount of water. The paste is then used to granulate the amorphous oxfendazole (with or without stabilizing polymer present), the lactose and remaining starch. The resulting granules are then dried, mixed with the magnesium stearate and then pressed into tablets.

(B) A tablet preparation suitable for administration to humans and other mammals was prepared with the following composition:

The preparation was prepared as follows: the powders are mixed together (with or without stabilizing polymer present) and pressed into tablets without further processing.

(C) A tablet preparation suitable for administration to cattle and similar mammals was prepared with the following composition:

The preparation was prepared in the following way: a paste is prepared from 7.5 mg of starch, the methylcellulose and the smallest possible amount of water. The paste is then used to granulate the amorphous oxfendazole (with or without stabilizing polymer present), the lactose and remaining starch. The resulting granules are then dried, mixed with the magnesium stearate and then pressed into tablets.

Example 9

Below is described an experimental procedure by means of which the effect of the new compounds can be demonstrated. (A) Fifteen goats are used, preferably from one and the same herd, which are known to be infected with nematode parasites, proven by positive counts of eggs in the faeces. The animals are preferably all of the same sex. They must be infested with goat parasite eggs and larvae, especially with Ostertagia spp.

(hereinafter referred to as "Ost") and Trichostrongylus spp. (hereinafter referred to as "Tri").

Treatment groups

1. Control

2. 9 mg of amorphous oxfendazole per kg

3. 15 mg oxfendazole per kg.

The animals are then subjected to necropsy on the 6th day after treatment. The gastrointestinal tract, lungs and liver are examined for nematodes and trematode parasites using standard parasitological methods.

(B) Sheep infested with nematodes with varying degrees of resistance to oxfendazole were treated with either levamisole, oxfendazole or amorphous oxfendazole according to the procedure described above.

The two studies mentioned above show that amorphous oxfendazole is approximately equivalent to oxfendazole in terms of effectiveness, but then in a reduced dose of only approx. 60% of that required for oxfendazole. No toxicity was detected for the indicated doses.

Example 10

An experimental procedure for

to determine the blood plasma concentrations of the active compounds administered.

Dogs were given orally either amorphous or crystalline oxfendazole at a dose of 10 mg/kg.

Blood samples were taken and analyzed before administration and on days 1, 2, 3, 7, 10 and 13 after administration. The area under the curve for plasma concentration deposited versus time was calculated. Dogs treated with amorphous oxfendazole showed a higher concentration of oxfendazole in plasma than dogs treated with oxfendazole in commercially available form.

A similar experiment with sheep showed similar increases of the area under the plasma concentration curve for amorphous oxfendazole compared to the area for crystalline oxfendazole.

Claims (14)

1. Process for the preparation of an amorphous compound of formula 1: or a pharmaceutically acceptable salt thereof, wherein R is lower alkyl; and R. is -S(0) R_, - OR. or 1 m 2 2 Y.(CH_) Y_R_ where 1 2 n 2 3 Y^ and Y^ are independently 0, S or S(0), R^ is lower alkyl, phenyl or naphthyl, and n is 1, 2, 3 or 4 ; R 2 is lower alkyl, cycloalkyl, alkenyl of from 3 to 7 carbon atoms, alkynyl of from 3 to 7 carbon atoms, phenyl, benzyl, phenylethyl or naphthyl; and m is 0 or 1, characterized by: A. (a) dissolving a compound of formula 1 in a base or acid to dissolve or solubilize the compound of formula 1 and then (b) adding an amount of an acid or base under such conditions that the compound of formula 1 precipitate in amorphous form, or B. (a) dissolve a compound of formula 1 in an acid or base to dissolve or solubilize the compound of formula 1, and then (b) spray-dry the solution from step (a) to form an amorphous compound of formula 1, or C (a) dissolves a compound of formula 1 in an acid or base in a first pH range to dissolve or solubilize the compound of formula 1 and then (b) adds a stabilizing amount of a stabilizing polymer in a solution with a second pH range opposite to that used in step (a), and then (c) adding acid or base to restore a third acidic or basic pH range on the same side of the pH scale as the first pH-o mrate to form an amorphous form of a compound of formula 1. 2. Method according to claim 1, characterized in that concentrated acetic acid, propionic acid, hydrochloric acid, phosphoric acid, formic acid or nitric acid is used as said acid. 3. Method according to claim 2, characterized in that concentrated hydrochloric acid or concentrated formic acid is used as acid. 4. Method according to claim 3, characterized in that concentrated formic acid is used as acid. 5. Method according to claim 1, characterized in that the pH range used in step A(a), B(a) or C(a) is lower than 3. 6. Method according to claim 1, characterized in that the pH range used in step A(a), B(a) or C(a) is between 8 and 10. 7. Method according to claim 1, characterized in that the pH range used in step A(b) or C(c) is between 4 and 6. 8. Method according to claim 1, characterized in that ammonium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, sodium methylate, sodium ethylate, sodium hydride, triethylamine or pyridine are used as the aforementioned base. 9. Method according to claim 8, characterized in that ammonium hydroxide or sodium hydroxide is used as the base. 10. Method according to claim 1, characterized in that the stabilizing polymer is selected from cellulose derivatives, polyvinylpyrrolidone and derivatives thereof, xanthan gums, pectins, alginates, gum tragacanth and derivatives thereof, gum arabic and derivatives thereof, carrageenans, agar and derivatives thereof, polysaccharides from microbial sources , arabinogalactans, galactomannans and dextrans. 11. Method according to claim 10, characterized in that a cellulose derivative is used as the stabilizing polymer. 12. Method according to claim 11, characterized in that methylcellulose, sodium carboxymethylcellulose, hydroxypropylmethylcellulose or hydroxypropylcellulose is used as cellulose derivative 13. Method according to claim 12, characterized in that methylcellulose is used as a cellulose derivative. 14. Process according to claim 1, for the production of amorphous oxfendazole, fenbendazole, albendazole, 5-n-propylsulfinyl-2-carbomethoxyaminobenzimidazole or oxibendazole, characterized in that the corresponding compound is used as starting material.