Published: June 2010

Interaction: Sodium valproate and carbapenems - new information

Prescriber Update 31(2): 14
June 2010

Prescribers are reminded of the clinically significant interaction between carbapenem antibiotics (such as imipenem, meropenem and ertapenem) and sodium valproate. Although this interaction is well established, international reports suggest it is more severe than initially thought.

The interaction has been reported to result in a 60-100% decrease in valproate plasma concentration within two days and reduced therapeutic effect. The underlying mechanism of action is yet to be explained.1

Monitoring valproate plasma levels or adjusting the dose is unlikely to manage this interaction given its extent and rapid onset. Prescribers are therefore advised to avoid the use of carbapenem antibiotics in patients taking sodium valproate.

New Zealand data sheets are currently being updated to strengthen the warnings about this interaction.

  1. European Medicines Agency. 28 January 2010. Monthly Report - Pharmacovigilance Working Party - January 2010 Plenary Meeting.