DK152119B - METHOD FOR PREPARING AETANOL-WATER SOLVATES OF ALKALIMETAL POLYMETAPHOSPHATE COMPLEXES OF ALFA-6-DESOXY-5-HYDROXYTETRACYCLINE - Google Patents

Description

The present invention relates to a process for the preparation of novel ethanol-water solvates of alkali metal polymetaphosphate complexes of α-6-deoxy-5-hydroxy-tetracycline, a compound also referred to as doxycycline, with the general formula set out in the preamble of claim 1, wherein Me, x, y and z have the same meanings stated, which have high stability and water solubility at 20 ° C> 4.5 mg / ml.

In Danish Patent Application No. 5166/71, preparation of alkali metal polymetaphosphate complexes of doxycycline is described. According to the present invention, improved products - said ethanol-water solvates - are prepared by proceeding as set forth in the characterizing portion of the patent claim.

For the preparation of polymethaphosphate complexes of doxycycline, doxycycline base is preferably used which is reacted in an inert organic solvent such as methanol, ethanol, ethyl acetate, dimethylformamide, dichloromethane, chloroform or mixtures thereof, preferably a mixture of methanol and chloroform. the sodium or potassium hydroxide is added as a methanolic solution. When the formation of the complex is complete, the ethanol-water solvate of the complex is precipitated with a non-solvent in the form of 95% ethanol, optionally. in admixture with isopropanol or preferably ethyl ether, isopropyl ether and / or hexane which is filtered.

The ethanol-water-solvate thus formed retains its biological activity illustrated in the above experiment # 3 for over 3 years without detectable decrease in room temperature storage, while the known doxycycline-alkali-metaphosphoric acid complex undergoes degradation to a degree of 3 -3.5% in 3 years at room temperature. The solvate in question thus has the advantage of being more stable than the corresponding non-solvated complex and is also well crystallized.

The polymeric nature of metaphosphoric acid (HPOg) n is known in that the degree of polymerization of the metaphosphoric acid is variable. The process of the present invention has the advantage over that described in DK Patent Application 5166/71 that the degree of polymerization of the complex produced does not vary, so that a substantially uniform, homogeneous complex is produced which allows precise dosing.

To prepare the complex, as stated in the claim, 6 moles of metaphosphoric acid (corresponding to 1 mole (HPO 1-5 moles of doxycycline, neutralizes to the desired degree with methanolic NaOH or KOH and precipitates the solvate with 95% ethanol, optionally. in admixture with another non-solvent.

The metaphosphoric acid is preferably prepared immediately before use. It can be advantageously prepared by dehydrating orthophosphoric acid, or by reacting phosphorus pentoxide with an equimolar amount of water in an inert organic medium such as those mentioned above.

The empirical formula of the solvent-free solvate-free complex confirmed by analysis is, when Me is Na, y and z = 5 and x = 1, identical to the formula for the hexametaphosphate sodium complex of doxycycline prepared by the method of U.S. Pat. U.S. Patent No. 2,791,609. However, the two complexes are different compounds, the polyphosphate complex of this invention being many times more soluble in water than the known hexametaphosphate sodium complex. In addition, the infrared absorption curves for the two complex groups show differences in the ranges 7.9-8.1 y and 9.2-9.6 y, which shows that the complex formation takes place in different ways.

The differences between the two groups of complexes in terms of solubility and the infrared curves show that the intramolecular structure is substantially different and it can be seen that the complexing mechanism as well as the groups of the doxycycline involved in this complexation are not identical for the two kinds of complexes.

For comparison and differentiation, both the metaphosphoric acid complexes and the acid addition salts of doxycycline were prepared in various molar ratios in accordance with U.S. Patent 3,053,892 and 3,200,149. For differentiation, the double salts with metaphosphoric acid as a cation with both doxycycline as well as sodium as anions were prepared in the manner described in Experiment 1. All of these complexes and acid addition salts have significantly lower solubility in water than the treated solvates of the alkali metal polymetaphosphate complexes, and the blood concentrations obtained after administration were quantitative and in terms of duration inferior to those obtained with the solvates. All the attempts made to convert the metaphosphoric acid addition salts of doxy-cyclin to the alkali metal polymetaphosphate complexes by treatment with aqueous sodium hydroxide or potassium hydroxide gave negative results.

The blood concentrations obtained after oral administration of simple mixtures of doxycycline hyclate and sodium hexametaphosphate as well as of doxycycline base monohydrate and sodium hexametaphosphate were significantly lower than those obtained after administration of the doxycycline hyclates herein. thus, the hexametaphosphate sodium salt does not enhance the absorption of doxycycline when administered concomitantly.

The ethanol-water solvates of the sodium or potassium poly-metaphosphate complexes of doxycycline as described herein have a favorable acute and chronic toxicity that is comparable to doxycycline and are pharmaceutically acceptable. The method of the present invention represents a significant step to improve the activity and clinical utility of doxycycline in increasing blood concentration when the doxycycline is administered in the form of the ethanol-water-solvates of alkali metal polymetaphosphate complexes. The main therapeutic benefit of the solvates of the alkali metal polymetaphosphate complexes of doxycycline is that the functional groups of doxycycline participating in the chelation of Ca and Mg ions are blocked in the solvates, as is shown in the above Experimental No. 2. Disadvantages associated with chelating tetracyclines are therefore significantly reduced when doxycycline is administered in the form of the ethanol-water-solvates of the doxycycline-alkali metal polymetaphosphate complexes produced by the process of the invention.

The solvates prepared by the process can be combined with other drugs with which they are incompatible.

The process according to the invention will now be illustrated by some examples. Following these, there are some experiments which, as mentioned above, illustrate the preparation of certain double salts and the fact that the solvates do not chelate with calcium and magnesium ions, and partly illustrate the serum concentrations of doxycycline after administration of the solvates, in comparison with the serum concentrations obtained by administration of doxycyklinhyklat.

Example 1 65 ml of methanol were added to 26 ml of chloroform containing 2.07 g of freshly prepared metaphosphoric acid and stirred for 30 minutes. Then, 10 g of doxycycline base monohydrate was added portionwise to the homogeneous solution of the metaphosphoric acid. Stirring was continued until a clear solution was obtained, after which 172 mg of sodium hydroxide dissolved in 4.7 ml of methanol was added which started precipitating the complex. After stirring for 15 minutes, 175 ml of 95% ethanol was added. The small amount of precipitate formed was redissolved and the mixture was slowly cooled in an ice-water bath. After 3 hours, a crystalline suspension was formed which was then filtered and dried at 40 ° C to yield 8.3 g of the polyphosphate-mono-sodium complex of doxycycline of formula (C22 H24N2 ° 8) 5 'NaPO .), - as a solvate with ethanol-water. Mp. 185-195 ° C.

Dissolve 1 g in 3 ml of water. E ^ cm = 302 at 268 mu. Optical rotation: [α] D = -85 ° (c = 1 in methanol containing 1% concentrated hydrochloric acid). Water content (Karl Fisher) 4%.

Example 2 250 ml of methanol were added to 250 ml of chloroform containing 20 g of metaphosphoric acid with stirring at room temperature, followed by the addition of 74.14 g of anhydrous doxycycline base (998.8 mcg / mg), 375 ml of methanol and 3.32 g of sodium hydroxide dissolved. in 45 ml of methanol. After stirring for 15 minutes, 1600 ml of 95% ethanol was added to complete the precipitate. The precipitate was then filtered, washed with ethanol and dried at 40 ° C to yield 68.7 g of the polyphosphate disodium complex of doxycycline of formula (C22H24N2 ° 8 ^ 4 '(HPO4)) as ethanol-water-solvate. * = 302 at 268 my and 242 at 349 my.

Example 3

To 4.74 g of freshly prepared metaphosphoric acid in 100 ml of chloroform was added with stirring 100 ml of methanol and stirring was continued for a further 15 minutes. Then, 50 ml of methanol was added followed by portion addition of 22.2 g of doxycycline base (992 mcg / g). The resulting clear solution was kept at a temperature not above 35 ° C. After stirring for one hour, 0.56 g of potassium hydroxide dissolved in 6 ml of methanol was added and then stirred for a further 15 minutes. The product was then crystallized by the addition of 400 ml of 95% ethanol and after 10 minutes 100 ml of ethyl ether was added. After one hour the product was filtered and dried and the yield was 19.1 g of polymethaphosphate-monocalcium complex of doxycycline of the formula (C22H24N2 ° 8 ^ 5 'KP037 ^^ oria clets ethanol-water-solvate, mp 191-194 ° C with decomposition, 1 g thereof 1 no.

dissolve in 2.8 ml of water or in 1.9 ml of 0.6% hydrochloric acid. = 294 at 268 microns and 231 at 349 microns (in methanol containing 1% concentrated hydrochloric acid).

Experiment 1

For differentiation purposes, the double salt of metaphosphoric acid was prepared as cation with both doxycycline as well as sodium as anions. The following experiments were carried out: 1.84 g of phosphorus pentoxide was weighed in 25.9 ml of chloroform to avoid prolonged contact with the air in a dry room and 0.25 ml of water was added and the mixture was stirred overnight. The chloroform was removed by distillation in vacuo and the thus obtained metaphosphoric acid was dissolved in 30 ml of water to which 10 g of doxycycline base monohydrate suspended in 40 ml of water was added. After one minute, the product was dissolved in a clear solution or stirred with 172 mg of sodium hydroxide dissolved in 5 ml of water. The obtained clear solution was immediately frozen in a mixture of acetone and dry ice and lyophilized. Melting point 199-202 ° C αβ = -95 ° (c = 1 in methanol containing 1% concentrated hydrochloric acid); 1%

Elcm = ve <^ 68 miJ ° 9 ^ 40 ve <^ ^ 49 my ^ methanol containing 1% concentrated hydrochloric acid.

100 mg of the product obtained above was dissolved in 3 ml of water from which slowly a compound which was not identical to either the hexametaphosphate of doxycycline nor the polyphosphate monosodium sodium of doxycycline began to precipitate.

Experiment 2

To demonstrate that the ethanol-water solvate of the polyphosphate monosodium complex of doxycycline binds to calcium phosphate to a lesser extent than doxycycline, the following experiments were performed: To 20 ml of a 1/100 molar aqueous solution of doxycycline hyclate were added 6 ml of N / 5 sodium bicarbonate and 6 ml. water at pH 7.1. After four hours, the solution was still clear, then to 29 ml of the described solution was added 0.5 g of calcium phosphate and the solution was stirred for one hour. The pH value at the end of this period was 8.1. Then the mixture was filtered and the doxycycline content of the filtrate was determined by ultraviolet absorption at 350 microns.

Similarly, the same experiment was conducted with 20 ml of aqueous solution of the ethanol-water solvate of the polyphosphate monosodium sodium complex of doxycycline obtained according to Example 1 and at a concentration of 6.3 g / l. The initial pH was 7.2 and the final pH was 7.95. The results were as follows:

Doxycycline content of the filtrate mcg / ml

Doxycycline Hyclate 271.2

Doxycycline-polyphosphate monosodium complex, ethanol-water-solvate 1184

It can be seen that the binding of the ethanol-water-sol-water of the polyphosphate mono-sodium complex of doxycycline with calcium phosphate is less than 1/4 relative to doxycycline about neutral pH.

Experiment 3

Gelatin capsules containing the ethanol-water solvate of the polyphosphate monosodium sodium complex of doxycycline (DMSC-EVS) prepared in accordance with Example 1 were prepared equivalent to 100 mg of doxycycline and capsules containing doxycycline hyclate (100 mg) were prepared.

A dose of 2 capsules was administered to 11 healthy subjects in a controlled trial to determine the serum concentrations of the ethanol-water-solvate of the complex compared to doxycycline hyclate. Blood samples were taken at 0, 2, 5 and 24 hours after administration of 2 x 100 mg capsules. Serum concentrations were determined in triplicate by microbiological pathway.

The results obtained are shown in Table 1. The ethanol-water-solvate administration of the polyphosphate monosodium sodium complex of doxycycline gave an average overall increase of nearly 50% of serum concentrations compared to those obtained after administration of docycycline hyclate.

TABLE 1

a) threw up after 1 hour and did not get DCH

b) vomited 1 hour after ingestion of both substances c) with ferrous sulfate, 100 mg x 2 in both cases

d) threw up after DCH

Claims (1)

Process for Preparation of Alkali Metal Poly-Metaphosphate Complexes of α-6-Deoxy-5-Hydroxytetracycline of the General Formula iC22H24N2 ° 8 ^ zf ^ MePO3 ^ x '(HPO3 ^ y' where ^ is sodium or potassium, x, y and z are whole numbers 1 to 5, x + y <6 and z <y, in the form of high stability ethanol-water solvates and a solubility in water at 20 ° C above 4.5 mg / ml, characterized by reacting 6 molar equivalents of metaphosphoric acid in a reaction-inactive organic solvent with 1-5 molar equivalents of α-6-deoxy-5-hydroxytetracycline, and then neutralize remaining unreacted free acid groups of metaphosphoric acid in whole or in part with a methanolic solution of sodium or potassium hydroxide. neutralization degree of stoichiometric equivalent amount to precipitate the ethanol-water complex of the complex thus formed by the addition of 95% ethanol or a reaction-inactive non-solvent containing 95% ethanol.