Co-administration of antiepileptic drugs in patients on antiretroviral therapy has not been well studied yet, and remains a therapeutic challenge. Drug interactions between antiepileptic drugs and antiretrovirals can arise from a number of mechanisms, including liver metabolism (increase or decrease), competition for protein binding and increase in viral replication. There is no strong evidence to guide clinicians at present.
The following points are important to remember when treating seizures and epilepsy in patients on ART:
- Great caution should be taken when using drugs metabolised in the liver by the cytochrome P450 enzyme system as this may cause alterations in levels of both AEDs and antiretrovirals leading to toxic or sub-therapeutic drug levels. This particularly pertains to the NNRTIs and more specifically to PIs.
- If clinically indicated, monitor AED levels in patients taking concurrent ART and AED therapy.
- Avoid prescribing carbamazepine, phenobarbital, and phenytoin for patients receiving NNRTIs or PIs, as there are serious P450 interactions involved. In this setting, consider lamotrigine and valproate. See: Epilepsy .
- Treat children on antiretrovirals presenting to casualty with acute seizures or in status epilepticus according to the existing standard status epilepticus or acute seizure protocols.
- Although benzodiazepines, phenytoin and phenobarbitone may interact with antiretroviral metabolism, the acute management of acute seizures or SE takes precedence in these instances.