Coadministration has not been studied but is not recommended. Quetiapine is primarily metabolised by CYP3A4 and coadministration with ketoconazole (a CYP3A4 inhibitor) increased quetiapine AUC by 5-8 fold. The European product label for quetiapine contraindicates quetiapine with CYP3A4 inhibitors (such as ritonavir). However, the US product label recommends that quetiapine should be reduced to one sixth of the original dose if coadministered with a potent CYP3A4 inhibitor. The decision to modify the dosage should be done in consultation with a specialist in mental health medicine as it could destabilize a patient. Given the mechanism-based inhibition of nirmatrelvir/ritonavir, the adjusted dose of quetiapine would have to be maintained up to 3 days after the last dose of nirmatrelvir/ritonavir. Similarly, if it is decided to pause quetiapine during nirmatrelvir/ritonavir treatment, quetiapine would have to be resumed 3 days after the last dose of nirmatrelvir/ritonavir.