Imipenem and meropenem: Comparison of in vitro activity, pharmacokinetics, clinical trials and adverse effects

To compare and contrast imipenem and meropenem in terms of in vitro activity, pharmacokinetics, clinical efficacy and adverse effects. MEDLINE search from 1975 to 1997 and follow-up of references. Clinical trials comparing imipenem with meropenem, or either imipenem or meropenem with standard therapy in the treatment of serious infections were selected. Imipenem, the first carbapenem, was first marketed in 1987; meropenem was introduced to the market in 1996. In general, imipenem is more active against Gram-positive cocci while meropenem is more active against Gram-negative bacilli. The agents display similar pharmacokinetics. Clinical studies in patients with serious infections (intra-abdominal infection, respiratory infection, septicemia, febrile neutropenia) report similar bacteriological and clinical cure rates with imipenem and meropenem. Meropenem is approved for the treatment of bacterial meningitis, whereas imipenem is not. Adverse effects are similar. Current literature supports the use of imipenem at a dose of 500 mg every 6 h and meropenem at 1 g every 8 h for the treatment of severe infections. For the treatment of serious infections, imipenem (500 mg every 6 h or 2 g/day [$98/day]) is more economical than meropenem (1 g every 8 h or 3 g/day [$142/day]) based on acquisition cost.