Aprepitant reduces the levels of ethinylestradiol and norethisterone (given as a combined hormonal contraceptive). Greater effects were seen in another study when
dexamethasone was also given with
aprepitant. Fosaprepitant, a prodrug of
aprepitant, would be expected to interact similarly.
Although the effects of these reduced contraceptive steroid levels on ovulation were not assessed, it is likely that they could result in reduced
efficacy. The manufacturer recommends that alternative or additional contraceptive methods should be used during
aprepitant therapy and for 2 months (UK advice) or one month (US advice) after the last dose of
aprepitant. For general advice on the use of
enzyme inducers and
contraceptives, see
contraceptives.