Pharmacokinetic study of cefmenoxime (SCE 1365-CMX) in healthy adults

Cefmenoxime pharmacokinetics were investigated in six healthy volunteers after intravenous and intramuscular administration of 0.5, 1, and 2 g. Blood and urine samples were analyzed by reversed-phase high-pressure liquid chromatography using ultraviolet detection at 275 nm. The assay is precise and linear up to 200 micrograms/ml-1, with 0.02 micrograms/ml-1 as the limit of detection. Linearity of cefmenoxime kinetics was demonstrated because the area under the plasma concentrations is proportional to studied doses. Eight hours after 1 g of cefmenoxime intramuscularly, mean plasma concentrations are, respectively, 0.6 +/- 0.1 and 0.3 +/- 0.1 microgram/ml-1. Intramuscular cefmenoxime is rapidly absorbed (Ka = 7.28 hours-1) with complete bioavailability (F = 0.99); apparent volume of distribution is 0.35 liters/kg-1 and elimination half-life 1.5 hours. The fraction of cefmenoxime excreted unchanged in the urine after intramuscular administration is 0.72, indicating a major contribution of renal clearance in total clearance. Experimental data after intramuscular administration were well fitted with a two-compartment model.