We present two case reports of drug interaction between valproic acid and meropenem. In comparison with expected population-kinetic based serum levels, we observed 90.8 and 93.5% decrease in valproic acid serum levels during concomitant administration with meropenem. If carbapenems need to be administered to valproic acid treated patient, other anticonvulsant addition seems to be the appropriate as most probably the valproic acid dose escalation would not be sufficient to achieve therapeutic serum concentration.
Keywords: Drug interaction; Meropenem; Therapeutic drug monitoring; Valproic acid.