Coadministration has not been studied and is contraindicated. Coadministration could potentially increase carbamazepine concentrations and significantly reduce darunavir/cobicistat concentrations which may result in loss of therapeutic effect and development of resistance. Alternative anticonvulsants should be considered. Limited data from a small number of patients showed TDM evaluations for carbamazepine and oxcarbazepine were within the therapeutic ranges and TDM results of darunavir were comparable with control values.

Coadministration with twice daily darunavir/ritonavir had no significant effect on darunavir exposure, but increased carbamazepine AUC by 45%. No a priori dose modification of darunavir/ritonavir or carbamazepine is recommended when initiating therapy, but patients should be monitored for potential carbamazepine related adverse events. Carbamazepine concentrations should be monitored; the carbamazepine dose may need to be reduced by 25% to 50% to achieve the desired clinical response. Limited data from a small number of patients showed TDM evaluations for carbamazepine and oxcarbazepine were within the therapeutic ranges and TDM results of darunavir were comparable with control values.