Coadministration has not been studied but based on limited data a clinically significant interaction is unlikely. Buprenorphine undergoes both N-dealkylation to form norbuprenorphine (via CYP3A4) and glucuronidation (via UGT2B7 and UGT1A1). Buprenorphine is also a substrate of P-gp. Concentrations of buprenorphine may increase due to mild inhibition of P-gp by velpatasvir, however, this is unlikely to be of clinical significance. Post hoc analysis of multiple clinical trials has revealed no impact on the occurrence of adverse effects in patients receiving buprenorphine with sofosbuvir-based therapies, including sofosbuvir/velpatasvir. No effect on sofosbuvir/velpatasvir concentrations is expected.