Coadministration of sofosbuvir and tenofovir (245 mg once daily) increased tenofovir Cmax by 25%, but decreased AUC and Cmin by 2% and 1%. Sofosbuvir Cmax decreased by 19% and 6%, whereas GS-331007 Cmax and AUC decreased by 23% and 16%. No dose adjustment of sofosbuvir or tenofovir-DF is required when sofosbuvir and tenofovir are used concomitantly.

The interaction between sofosbuvir and tenofovir was evaluated in clinical trials and no dose adjustment is needed for either drug. Coadministration of tenofovir (300 mg once daily with emtricitabine and efavirenz) and sofosbuvir (400 mg single dose) was studied in 16 subjects. Sofosbuvir Cmax and AUC decreased by 19% and 6%, respectively, with GS-331007 Cmax and AUC decreasing by 23% and 16%, respectively. Tenofovir Cmax increased by 25%, but AUC and Cmin decreased by 2% and 1%, respectively.

 

Coadministration of a single dose of sofosbuvir (400 mg) before and after 14 days of Atripla (efavirenz/emtricitabine/tenofovir 600/200/300 mg once daily) was studied in 16 subjects. Cmax of sofosbuvir and GS-331007 were slightly decreased (~20-23%) in the presence of Atripla. Sofosbuvir slightly increased tenofovir Cmax (~25%), but did not affect emtricitabine or efavirenz. 

No clinically significant pharmacokinetic drug interactions between sofosbuvir (GS-7977) and HIV antiretrovirals Atripla, rilpivirine, darunavir/ritonavir, or raltegravir in healthy volunteers. Kirby B, et al. Hepatology, 2012, 56(4); 1067A (abstract 1877).