[Pharmacokinetic interaction between valproic acid and meropenem]

Several reports have described a decrease in valproic acid (VPA) serum concentrations when carbapenem therapy is administered. The exact mechanism of this pharmacokinetic interaction is unknown, although several experimental studies have been carried out in animals. Because of these interactions, plasma concentrations of VPA in these patients should be monitored and, whenever possible, VPA or carbapenem therapy should be substituted by other drugs. We describe the cases of two epileptic children who simultaneously received meropenem and VPA. Concentrations of VPA decreased to subtherapeutic levels. We review the various mechanisms for this interaction proposed to date, as well as all reported cases.