Coadministration has not been studied. Doravirine is metabolized by CYP3A4 and coadministration may increase doravirine concentrations due to inhibition of CYP3A4 by atazanavir. Coadministration with ritonavir (a strong inhibitor of CYP3A4) increased doravirine exposure by ~3.5-fold. No dose adjustment of doravirine is required as phase I trials showed a good tolerability of doravirine with up to a 3-4 fold increase in exposure.