Valproic acid（VPA）為建議監測血中濃度的抗癲癇藥，影響其濃度的藥品有macrolide類抗生素、rifampin、及抗癲癇藥品carbamazepine、lamotrigine、phenytoin…等。VPA併用carbapenem類抗生素，使其藥物血中濃度降低的情況，近年來也廣泛的被探討。此案例為一64歲男性病患，使用VPA治療癲癇，於兩次住院分別併用ertapenem及tienam（imipenem 500 mg/ cilastatin 500mg）。在併用期間，皆於數天內觀察到VPA血中濃度降低之情形；影響情況分別由34.94μg/ml降至3.0μg/ml、45.98μg/ml降至29.3μg/ml。此案例顯示出VPA與carbapenem類藥品間交互作用之顯著性，推測其可能機轉為加速VPA的代謝、抑制VPA代謝物水解回VPA或是將VPA留在紅血球中。建議日後若併用VPA與carbapenem類藥品，須監測VPA之血中濃度，甚至更換藥品以避免此交互作用，造成病情控制不佳。

Valproic acid (VPA) is an anticonvulsant and is recommend to monitor drug level during treatment for efficacy and safety concern. It is well known that combined use of valproic acid and macrolide antibiotics, rifampin, carbamazepine, lamotrigine or phenytoin will affect serum concentration of VPA. In addition, cases discussed about the serum VAP concentration caused by carbapenem antibiotics were published recently. We report this 64-year-old male case, whom treated with VPA for seizure control. Two carbapenems, ertapenem and tienam (imipenem 500mg/ cilastatin 500mg) were prescribed separately in the hospitalization. During the combination use of VPA and carbapenems, the serum level of VPA fell from 34.94 μg/ml to 3.0 μg/ml and 45.98 μg/ml to 29.3 μg/ml within several days. Our case revealed the significance of drug interaction between VPA and carbapenems. Three hypotheses may explain the interaction (a) increase VPA metabolism, (b) decrease VPA quantity liberated from VPA metabolites, and (c) retain VPA in red blood cell. In conclusion, we strongly suggest to monitor the drug level of VPA, when VPA and carbapenems used concurrently, and modify the regimen if indicated.