Do Not Coadminister
Emtricitabine/Tenofovir-DF (FTC/TDF, PrEP)
Quality of Evidence: Very Low
Coadministration is not recommended in the European product label due to increased didanosine concentrations (40-60% increase in systemic exposure) and toxicity. The US product label for emtricitabine/tenofovir-DF recommends close monitoring for didanosine-associated adverse events and a reduced dose of didanosine (250 mg once daily for adults weighing 60 kg or greater with creatinine clearance 60 mL/min or greater; 200 mg once daily for adults weighing less than 60 kg with creatinine clearance 60 mL/min or greater). However, a decreased dosage of 250 mg didanosine with tenofovir-DF has been associated with reports of high rates of virological failure within several tested combinations. Coadministration with emtricitabine has not been studied. There have been reports of a high rate of virological failure and of emergence of resistance at early stage when tenofovir-DF was combined with lamivudine and didanosine as a once daily regimen. A similar outcome would be expected if emtricitabine/tenofovir-DF was combined with a third NRTI.