No Interaction Expected
Emtricitabine/Tenofovir-DF (FTC/TDF, PrEP)
Quality of Evidence:
Coadministration with norgestimate as hormone replacement therapy (HRT) has not been studied but based on metabolism and clearance a clinically significant interaction is unlikely. Norgestimate is deacetylated to the active metabolite norelgestromin which is then metabolised to norgestrel, possibly by CYP3A4. Emtricitabine or tenofovir-DF do not interact with these metabolic pathways. In addition, no interaction is expected with estradiol or estrogens administered as part of HRT. No clinically significant interactions were observed with tenofovir and norgestimate/ethinylestradiol administered as an oral contraceptive.
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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