Coadministration of tenofovir (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 darunavir coadministered with low dose ritonavir is given in combination with tenofovir, particularly in patients with underlying systemic or renal disease, or in patients taking nephrotoxic agents.
Prezista Summary of Product Characteristics, Janssen-Cilag Ltd, June 2012.

The interaction between darunavir/ritonavir and tenofovir was evaluated in clinical studies and no dose adjustment is needed for either drug. 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. Darunavir/ritonavir and tenofovir disoproxil fumarate can be coadministered without any dose adjustments.
Prezista Prescribing Information, Tibotec Inc, June 2012.

When tenofovir disoproxil fumarate (300 mg once daily) was administered with darunavir/ritonavir (300/100 mg twice daily), there was no sigificant effect on darunavir/ritonavir PK parameters. Tenofovir AUC increased by 22% and Cmin increased by 37%. No dose adjustment is recommended. The increased exposure of tenofovir could potentiate tenofovir associated adverse events, including renal disorders. Renal function should be closely monitored.
Viread Summary of Product Characteristics, Gilead Sciences Ltd, September 2016.

Darunavir coadministered with ritonavir have been shown to increase tenofovir concentrations. Coadministration of darunavir/ritonavir (300/100 mg twice daily) and tenofovir-DF (300 mg once daily) was studied in 12 subjects. Tenofovir Cmax, AUC and Cmin increased by 24%, 22% and 37%, respectively; darunavir Cmax, AUC and Cmin increased by 16%, 21% and 24%, respectively. Patients receiving tenofovir-DF concomitantly with ritonavir-boosted darunavir should be monitored for tenofovir-associated adverse reactions. Tenofovir-DF should be discontinued in patients who develop tenofovir-associated adverse reactions.
Viread Prescribing Information, Gilead Sciences International Inc, February 2016.