GB806929A - Purification of alkali metal salts of phenoxymethylpenicillin - Google Patents

Abstract

Alkali metal salts of phenoxymethylpenicillin, free or substantially free from coloured impurities and of high potency, are obtained by treating an aqueous solution of an alkali metal salt of phenoxymethylpenicillin with a corresponding alkali metal salt and allowing the alkali metal salt of phenoxymethylpenicillin to separate therefrom. It is preferred that the starting material contains between 100,000 and 200,000 units of phenoxymethylpenicillin per millilitre and that the corresponding alkali metal salt be present in the reaction mixture in a concentration of about 30 per cent. The alkali metal salt may be added to the aqueous penicillin solution in the form of the anhydrous salt or, if very soluble in water, in the form of a concentrated aqueous solution thereof. The aqueous penicillin solution may be prepared by dissolving an alkali metal salt of phenoxymethylpenicillin in water, or by extracting an organic solvent solution, e.g. butyl acetate solution containing phenoxymethylpenicillin with an aqueous solution of an alkali metal bicarbonate, e.g. potassium bicarbonate. In examples, potassium phenoxymethylpenicillin is obtained by adding to an aqueous solution of crude potassium phenoxymethylpenicillin (a) anhydrous potassium acetate, (b) a concentrated aqueous solution of potassium acetate, or (e) potassium chloride. Sodium phenoxymethylpenicillin is obtained by adding to an aqueous solution of crude sodium phenoxymethylpenicillin (a) anhydrous sodium acetate or (b) sodium chloride.