Coadministration had no significant effect on dolutegravir exposure (AUC and Ctrough decreased by 5% and 30% due to induction of UGT1A1 and CYP3A, Cmax increased by 16%). No dose adjustment is necessary.

Tivicay Summary of Product Characteristics, ViiV Healthcare, March 2019. 

 

Based on drug interaction trial results, rifabutin can be coadministered with dolutegravir without a dose adjustment. Coadministration of rifabutin (300 mg once daily) and dolutegravir (50 mg once daily) to 9 subjects increased dolutegravir Cmax by 16%, but decreased AUC and Ctrough by 5% and 30%.

Tivicay US Prescribing Information, ViiV Healthcare, July 2019. 

 

Coadministration of dolutegravir alone (50 mg once daily) and with rifabutin (300 mg once daily) was evaluated in 9 HIV-negative subjects. Rifabutin decreased dolutegravir AUC by 5% and Ctrough by 30%, but increased Cmax by 15%. The decrease in dolutegravir Ctrough is unlikely to be clinically significant given the known PK/PD relationships and data from phase 2b dose ranging studies.