Coadministration with ritonavir decreased ethinyl estradiol AUC and Cmax by 40% and 32%. Due to reductions in ethinyl estradiol concentrations, barrier or other non-hormonal methods of contraception should be considered during the 5 days of Paxlovid treatment and until one complete menstrual cycle after stopping Paxlovid. Ritonavir is likely to change the uterine bleeding profile and reduce the effectiveness of estradiol-containing contraceptives.

Coadministration with ritonavir decreased ethinyl estradiol AUC and Cmax by 40% and 32%. Due to reductions in ethinyl estradiol concentrations, barrier or other non-hormonal methods of contraception should be considered with concomitant ritonavir use at high dose in accordance with its previous use as an antiretroviral agent or as a pharmacokinetic enhancer. Patients using combined hormonal contraceptives should be advised to use an effective alternative contraceptive method or an additional barrier method of contraception during treatment with Paxlovid, and until one menstrual cycle after stopping Paxlovid. Ritonavir is likely to change the uterine bleeding profile and reduce the effectiveness of estradiol-containing contraceptives.

Co-administration may decrease ethinyl estradiol concentrations. An additional, non-hormonal method of contraception should be considered during the 5 days of Paxlovid treatment and until one menstrual cycle after stopping Paxlovid.