Imipenem/cilastatin: evolution of the sustained-release intramuscular formulation.

Since 1983, numerous studies have confirmed the efficacy of imipenem/cilastatin as monotherapy for polymicrobial and multiresistant infections. Doses range from 1 to 4 g/day, usually given in 3-4 intravenous infusions. Recently, a sustained-release, intramuscular formulation of imipenem/cilastatin sodium has been developed. Investigations in both animals and healthy human volunteers have shown that this formulation maintains plasma concentrations of imipenem above susceptibility breakpoints for nearly twice the duration provided by similar intravenous doses. Although peak concentrations are lower with the intramuscular formulation, current research suggests that the efficacy of beta-lactam antibiotics is more closely related to the duration that levels are sustained above minimum inhibitory concentrations, rather than to the magnitude of peak concentrations over minimum inhibitory concentrations. Hence, the intramuscular formulation of imipenem/cilastatin sodium holds promise as an efficient, effective regimen in patients with serious infections of mild to moderate severity.