Clinically significant pharmacokinetic drug interactions of antiepileptic drugs with new antidepressants and new antipsychotics

Antiepileptic drugs (AEDs) are frequently co-prescribed with new antidepressants (ADs) or new antipsychotics (APs). A PubMed search with no time limit was used to update the review of the clinically significant pharmacokinetic (PK) drug interactions DIs (DIs) between AEDs with new ADs and APs. Our best interpretation of what to expect regarding dosing changes in the average patient after combining AEDs with new ADs or new APs is summarized on updated tables that integrate the information on in vitro metabolism studies, therapeutic drug monitoring (TDM) studies, case report/series and prospective studies. There will be a need to periodically update these dose correction factors as new knowledge becomes available. These tables will provide some orientation to clinicians with no TDM access and may also encourage clinicians to further study TDM. The clinical relevance of the inductive properties of carbamazepine, phenytoin, phenobarbital and primidone on new ADs and new APs and the inhibitory properties of valproic acid and some new ADs, are relatively well understood. On the other hand, PK DI studies combining new AEDs with weak inductive properties (particularly oxcarbazepine doses ≥ 1200 mg/day), topiramate doses ≥ 400 mg/day, clobazam, eslicarbazepine, and rufinamide), with new ADs and new APs are needed. Valproic acid may be 1) an inhibitor and/or inducer of clozapine and olanzapine with potential for clinically relevant DIs, 2) an inhibitor of paliperidone, and 3) a weak inducer of aripiprazole. Fluoxetine and fluvoxamine are relevant inhibitors of phenytoin and valproic acid and possibly of clobazam, lacosamide, phenobarbital, or primidone.