Lowering Serum Concentration of Valproic Acid with the Concomitant Use of Carbapenems

Two critically ill patients presented a rapidly drop of serum valproic acid concentrations with the concomitant use of carbapenem antibiotics (meropenem and imipenem). Previously well-controlled seizure episodes reoccurred after adding carbapenem antibiotics for treating nosocomial infections. The lowering of serum levels of valproic acid was observed even at an increasing dose of valproic acid. The seizure episodes were subsided and the serum concentrations of valproic acid returned to therapeutic levels when carbapenems were discontinued. The literature reported potential mechanisms of the interaction between valproic acid and carbapenems were reviewed.