No Interaction Expected
Emtricitabine/Tenofovir-DF (FTC/TDF, PrEP)
Norethisterone [Norethindrone] (COC)
Quality of Evidence:
Coadministration of a combined oral contraceptive (COC) containing norethisterone and mestranol or ethinylestradiol has not been studied but based on metabolism and clearance a clinically significant interaction is unlikely. Norethisterone is metabolized by CYP3A4. Mestranol is rapidly and almost completely converted to ethinylestradiol by CYP2C9; ethinylestradiol is mainly metabolised by hydroxylation. Emtricitabine/tenofovir-DF does not interact with these metabolic pathways. No clinically significant drug interactions were observed when tenofovir-DF was coadministered with a COC containing ethinylestradiol/norgestimate.
Coadministration of norgestimate/ethinylestradiol was studied with tenofovir disoproxil fumarate. Norgestimate AUC and Cmax decreased by 4% and 5%; ethinyl oestradiol AUC, Cmax and Cmin decreased by 4%, 6% and 2%, respectively. No dose adjustment of norgestimate/ethinyl estradiol is required.
Truvada Summary of Product Characteristics Gilead Sciences Ltd, June 2018.
No clinically significant drug interactions have been observed between TDF and oral contraceptives.
Truvada US Prescribing Information, Gilead Sciences Inc, May 2018.
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