STABILITY AND KINETICS OF DEGRADATION OF IMIPENEM IN AQUEOUS-SOLUTION

In weakly acidic solution, the broad‐spectrum antibiotic imipenem undergoes complex oligomerization initiated by intermolecular carboxyl group attack on the β‐lactam group. In weakly alkaline solution, intermolecular reaction between the β‐lactam and formimidoyl groups occurs instead. Both β‐lactam and formimidoyl groups also hydrolyze at pH‐dependent rates. Complex decomposition schemes were determined in kinetic studies at pH 4.0 and 9.0–9.5 using HPLC and mathematical models. The rates of the several initial reactions, calculated as functions of pH and imipenem concentration by fitting the models to kinetic data, fully account for imipenem decomposition rates throughout the neutral pH range. Copyright © 1990 Wiley‐Liss, Inc., A Wiley Company