Concomitant treatment with lopinavir/ritonavir is contraindicated. Coadministration of darunavir/ritonavir and lopinavir (400/100 mg twice daily) increased lopinavir AUC (9%) and Cmin (23%), but decreased Cmax by 2%. Based upon non dose normalised values, darunavir AUC, Cmax and Cmin decreased by 38%, 21% and 51%, respectively. Coadministration of darunavir and lopinavir/ritonavir (533/133 mg twice daily) had no effect on lopinavir AUC, but increased Cmax (11%) and Cmin (13%). Darunavir AUC, Cmax and Cmin decreased by 41%, 21% and 55%, respectively. Due to a decrease in the exposure (AUC) of darunavir by 40%, appropriate doses of the combination have not been established. Hence, concomitant use of boosted darunavir and the combination product lopinavir/ritonavir is contraindicated.

Coadministration of lopinavir/ritonavir (400/100 mg twice daily) and darunavir/ritonavir (1200/100 mg twice daily) was studied in 14 subjects and compared to PK parameters obtained with darunavir/ritonavir 600/100 mg twice daily. Darunavir exposure decreased and lopinavir exposure increased. Cmax, AUC and Cmin of darunavir decreased by 21%, 38% and 51%, respectively. Lopinavir Cmax decreased by 2%; AUC and Cmin increased by 9% and 23%, respectively. Coadministration of lopinavir/ritonavir (533/133 mg twice daily) and darunavir (1200 mg twice daily) was studied in 15 subjects and compared to PK parameters obtained with darunavir/ritonavir 600/100 mg twice daily. Darunavir Cmax, AUC and Cmin decreased by 21%, 41% and 55%, respectively. Lopinavir Cmax, AUC and Cmin increased by 11%, 9% and 13%, respectively. Appropriate doses of the combination have not been established. Hence, it is not recommended to co-administer lopinavir/ritonavir and darunavir, with or without ritonavir. 

According to current treatment guidelines, dual therapy with protease inhibitors is generally not recommended.