Reduced Valproic Acid Concentrations in Patients Receiving Carbapenems
This study evaluates the impact of coadministering carbapenem antibiotics with valproic acid (VPA) and uses model-based simulations to determine if dose adjustments can maintain therapeutic levels.
A systematic review and meta-analysis of 13 clinical studies and 15 case reports confirmed that carbapenem antibiotics, including meropenem, ertapenem, and imipenem significantly reduce valproic acid (VPA) serum concentrations by 60-90%. This interaction occurs rapidly, often within one to thirty days of coadministration, and can lead to sub-therapeutic levels that resulted in breakthrough seizures for nearly 30% of patients analysed. While model-based simulations show that increasing VPA dosages to approximately 25mg/kg/day might reach therapeutic targets, such high doses significantly increase the risk of drug toxicity and side effects because VPA clearance also increases alongside the dose.
Consequently, clinicians are advised to avoid this combination whenever possible by choosing alternative antibiotics or switching to a non-interacting antiepileptic medication.
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