Coadministration has not been studied. Quetiapine is primarily metabolized by CYP3A4 and coadministration with ketoconazole (a CYP3A4 inhibitor) increased quetiapine AUC by 5-8 fold. Emtricitabine and tenofovir alafenamide do not interact with this metabolic pathway. The European SmPC for Symtuza contraindicates coadministration with quetiapine. However, the US prescribing information for Symtuza recommends that quetiapine should be reduced to one sixth of the original dose if coadministration is necessary and use of an alternative antiretroviral is not possible. [This interaction checker reflects the more cautious option.]