Potential Weak Interaction
Emtricitabine/Tenofovir-DF (FTC/TDF, PrEP)
Quality of Evidence:
Coadministration with emtricitabine/tenofovir-DF has not been studied. Based on metabolism and clearance a clinically significant interaction with emtricitabine is unlikely. Coadministration of tenofovir-DF (300 mg once daily) and abacavir (300 mg single dose) had no effect on abacavir AUC but Cmax increased by 12%. A similar increase in abacavir Cmax may occur with emtricitabine/tenofovir-DF. A high rate of virological failure and emergence of resistance have been reported when lamivudine was combined with tenofovir-DF and abacavir as a once daily regimen. A similar outcome is anticipated if emtricitabine/tenofovir-DF is combined with a third NRTI.
There have been reports of a high rate of virological failure and of emergence of resistance at an early stage in HIV-1 infected patients when tenofovir disoproxil was combined with lamivudine and abacavir as well as with lamivudine and didanosine as a once daily regimen. There is close structural similarity between lamivudine and emtricitabine and similarities in the pharmacokinetics and pharmacodynamics of these two agents. Therefore, the same problems may be seen if Truvada is administered with a third nucleoside analogue.
Truvada Summary of Product Characteristics Gilead Sciences Ltd, June 2018.
Coadministration of abacavir (300 mg once daily) and tenofovir-DF (300 mg once daily) increased abacavir Cmax by 12%, but had no effect on AUC (n=8).
Truvada US Prescribing Information, Gilead Sciences Inc, May 2018.
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