Coadministration with emtricitabine has not been studied. Based on the different elimination pathways of the other NRTIs zidovudine, emtricitabine, stavudine, lamivudine, that are primarily renally excreted, no interactions are expected for these medicinal compounds and boosted darunavir. Boosted darunavir can be used with these NRTIs without dose adjustment. Coadministration of tenofovir-DF (300 mg once daily) and darunavir/ritonavir (at a dose lower than recommended or with a different dosing regimen) increased tenofovir AUC, Cmax and Cmin by 22%, 24% and 37%, respectively. Darunavir AUC, Cmax and Cmin increased by 21%, 16% and 24%, respectively. The increase in tenofovir is from an effect on MDR1 transport in renal tubules. Monitoring of renal function may be indicated when boosted darunavir is given in combination with tenofovir, particularly in patients with underlying systemic or renal disease, or in patients taking nephrotoxic agents.

No dosage adjustments are recommended when darunavir/ritonavir is co-administered with emtricitabine or tenofovir-DF. Coadministration of tenofovir (300 mg once daily) and darunavir/ritonavir (300/100 mg twice daily) was studied in 12 subjects. Darunavir and tenofovir exposure was increased. Darunavir Cmax, AUC and Cmin increased by 16%, 21% and 24%, respectively. Tenofovir Cmax, AUC and Cmin increased by 24%, 22% and 37%, respectively.