Esters of cephalosporins. Part III. Separation and properties of the R and S isomers of the 1-acetoxyethyl ester of cefuroxime.

Two separation methods for the R and S isomers of the 1-acetoxyethyl ester of cefuroxime [I] were evaluated. Physico-chemical and biological properties of these isomers were studied. It was found that the R isomer after oral administration to rats is absorbed better and faster than the isomer S.

Esters of cephalosporins. Part II. Differences in the properties of various forms of the 1-acetoxyethyl ester of cefuroxime.

Physico-chemical and microbiological properties of three different forms (crystalline and two amorphous ones) of the 1-acetoxyethyl ester of cefuroxime and bioavailability after oral administration to rats have been investigated. Relation between physico-chemical properties of these forms and their bioavailability is observed. It is shown, that for oral administration the most appropriate is an amorphous form obtained by rapid evaporation of a solvent from solution of the ester.