Abstract: There is presented a method, in the form of a dosage formulation, for transforming substantially orally inactive .beta.-lactam antibiotics or their pharmaceutically acceptable salts or the esters, ethers, or hydrates of said antibiotics or their salts into orally active compounds by combination of the chosen .beta.-lactam antibiotic with an enhancer comprising an aliphatic, preferably a C.sub.2 to C.sub.18, straight- or branched-chain, saturated or unsaturated, fatty acid or an aliphatic, preferably a C.sub.2 to C.sub.12, straight- or branched-chain, saturated or unsaturated, fatty acid mono-, di- or triglyceride or mixtures thereof, partial or total esters of propylene glycol, polyethylene glycol and carbohydrates of C.sub.2 to C.sub.12 fatty acids, as well as the pharmaceutically acceptable esters and ethers of said glycerides. The antibiotic and enhancer mixture may be administered orally as a solid dosage form with the .beta.