Coadministration has not been studied and is not recommended. Dasatinib is metabolised by CYP3A4 and concentrations are expected to increase due to strong inhibition of CYP3A4 by nirmatrelvir/ritonavir. Ketoconazole (a strong CYP3A4 inhibitor) increased dasatinib AUC by 5-fold. A similar effect is expected with nirmatrelvir/ritonavir and coadministration with strong CYP3A4 inhibitors is not recommended. Nirmatrelvir/ritonavir and dasatinib should not be coadministered in patients with accelerated or blast phase chronic myelogenous leukaemia (CML). For this particular indication, maintain dasatinib treatment and use an alternative COVID-19 therapy. In chronic phase CML, the decision to pause or dose adjust dasatinib should be made in conjunction with the patient’s oncologist. Restart dasatinib 3 days after completing nirmatrelvir/ritonavir treatment given that CYP3A4 inhibition takes several days to resolve. Alternatively, if coadministration is necessary, consider reducing dasatinib dose to 40 mg (in patients taking dasatinib 140 mg once daily) and to 20 mg (in patients taking dasatinib 100 or 70 mg once daily) with close monitoring for toxicity.