Coadministration has not been studied but based on metabolism and clearance a clinically significant interaction is unlikely and contraceptive efficacy is unlikely to be affected. Ethinylestradiol is mainly metabolized by hydroxylation with CYP3A4 and CYP2C9. Gestodene is metabolized by CYP3A4 and to a lesser extent by CYP2C9 and CYP2C19. Sofosbuvir does not affect CYP enzymes. Sofosbuvir is a prodrug and formation of its active metabolite is unlikely to be affected by comedications. Coadministration of sofosbuvir and an oral contraceptive containing ethinylestradiol and another progestogen, norgestimate was studied. There were no clinically relevant changes in the concentrations of ethinylestradiol, norelgestromin or norgestrel.