Coadministration has not been studied. Flucloxacillin is mainly eliminated renally, partly by glomerular filtration and partly by active secretion by OAT1. Sofosbuvir and velpatasvir are substrates of P-gp and BCRP. Velpatasvir is also a substrate of OATP1B and CYP2B6, 2C8, and 3A4. Flucloxacillin is thought to be a weak inducer of CYP3A4 and P-gp, particularly at higher doses (>2-3 g daily). A modest reduction in plasma concentrations of sofosbuvir/velpatasvir may be observed but this is unlikely to be clinically relevant unless flucloxacillin is prescribed at higher doses for a prolonged course (>10-14 days).