Imipenem Valproate

Panipenem/betamipron dramatically reduced the valproate serum levels of 6 patients. Imipenem and meropenem have similar effects and seizures have occurred when they were given to patients taking valproate. Ertapenem is predicted to interact similarly. 

A report describes a reduction in valproate levels from 80 micrograms/mL to 24 then 33 micrograms/mL in an epileptic patient 4 and 11 days after imipenem was given to treat a Pseudomonas aeruginosa infection. ... 

Although there is only an isolated report of an interaction between valproate and imipenem, there are now several reports of the interaction between valproate and meropenem or panipenem. Seizures or increased seizure frequeney have been reported. It would therefore seem prudent to monitor the valproate levels in any patient also given carbapenems, being alert for the need to increase the valproate dosage, or to use another antibacterial, or an alternative to valproate. Carbamazepine and phenytoin did not interact in the above reports. The manufacturers of ertapenem have no reports of an interaction on their files, but prudently warn about a possible interaction with valproate because of the interactions seen with other carbapenems. 

Carbapenems An old Chinese man with epilepsy had seizures when meropenem was added to treatment with valproate [407 ]. In a retrospective study of six critically ill patients taking valproate who concurrently received meropenem (n = 4), imipenem (n = 1), or ertapenem (n = 1) mean plasma valproate trough concentrations fell by 58% and estimated mean valproate clearance increased by 191% compared with values obtained while they were not receiving a carbapenem five patients had generalized seizures during concurrent valproate -b carbapenem treatment, including two with no prior history of seizures [408 ]. Meropenem is an enzyme inducer. Because of this pharmacokinetic interaction, concurrent use of these medications should be avoided. 

---