Coadministration had no effect on tenofovir alafenamide concentrations but increased tenofovir concentrations. The recommended dose of emtricitabine/tenofovir alafenamide is 200/10 mg once daily when used with boosted darunavir.

No dosage adjustments are recommended when darunavir/ritonavir is co-administered with emtricitabine/tenofovir alafenamide.

When given with darunavir with ritonavir or cobicistat for HIV-treatment, the dose of Descovy is 200/10 mg once daily. Co-administration of Descovy with medicinal products that inhibit P-gp and BCRP activity (e.g., cobicistat or ritonavir) are expected to increase the absorption and plasma concentration of tenofovir alafenamide. Coadministration of darunavir/cobicistat (800/150 mg once daily), emtricitabine and tenofovir alafenamide (25 mg once daily) had no effect on the AUC and Cmax of tenofovir alafenamide, but increased tenofovir AUC, Cmax and Cmin by 224%, 216% and 221%, respectively. There was no change in darunavir AUC, Cmax and Cmin. Coadministration of darunavir/ritonavir (800/100 mg once daily) and tenofovir alafenamide (10 mg once daily) had no effect on the AUC and Cmax of tenofovir alafenamide, but increased tenofovir AUC and Cmax by 105% and 142%. There was no change in darunavir AUC, Cmax and Cmin.

Based on drug interaction studies conducted with the components of Descovy, no clinically significant drug interactions have been either observed or are expected when Descovy is combined with darunavir with ritonavir or cobicistat. Coadministration darunavir/cobicistat (800/150 mg once daily) and tenofovir alafenamide (25 mg once daily, dosed as Descovy) was studied in 11 subjects. Tenofovir alafenamide Cmax and AUC decreased by 7% and 2%; darunavir Cmax increased by 2%, but AUC and Cmin decreased by 1% and 3%. Coadministration of darunavir/ritonavir (800/100 mg once daily) and tenofovir alafenamide (10 mg once daily) was studied in 10 subjects. Tenofovir alafenamide Cmax and AUC increased by 42% and 6%; darunavir Cmax decreased by 1%, but AUC and Cmin increased by 1% and 13%.

Coadministration of darunavir/ritonavir (800/100 mg once daily) with emtricitabine/tenofovir alafenamide (200/10 mg once daily) was studied in 10 healthy volunteers in a crossover study. Tenofovir alafenamide AUC and Cmax increased by 4% and 42%, respectively. Tenofovir AUC and Cmax increased by 105% and 142%, respectively. Darunavir pharmacokinetic parameters were similar to historical controls. The authors hypothesise that the increase in tenofovir alafenamide and tenofovir exposures are due to intestinal inhibition of P-gp and/or BCRP by ritonavir. Coadministration of darunavir/ritonavir with tenofovir alafenamide is supported by tenofovir alafenamide safety data.