Coadministration has not been studied. Clozapine is metabolized by CYPs 1A2, 2C19, 3A4, and to a lesser extent by CYPs 2C9 and 2D6. Nirmatrelvir/ritonavir could potentially increase clozapine exposure. The British and American product labels for Paxlovid advise if coadministration is necessary to consider reducing the clozapine dose and to monitor for adverse reactions. Whereas, the European product label for Paxlovid advises that given the risk of increase in clozapine exposure and thus of its related adverse events, coadministration should not be used unless a multidisciplinary consultation could be obtained to safely guide it.