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• Dolutegravir (DTG) and darunavir/ritonavir (DRV/r) are potent and favourable options for treatment of human immunodeficiency virus infection. • The glucuronidation metabolic ratio of DTG increased when co-administered with DRV/r, probably due to ritonavir. • The effect of DRV/r co-administration on total and trough exposure of twice-daily DTG was investigated. • DRV/r and DTG performance during the highly viraemic phase of acute HIV infection was studied. To the authors' knowledge, there is currently no literature or guidance recommendation regarding whether the dose of dolutegravir (DTG) should be increased when co-administered with darunavir/ritonavir (DRV/r) in patients with acute human immunodeficiency virus infection (AHI). This study assessed the pharmacokinetics (PK) of twice-daily (BID) DTG and once-daily (QD) DRV/r, and compared this with DTG QD without DRV/r in patients with AHI. Forty-six participants initiated antiretroviral therapy within <24 h of enrolment: DTG 50 mg BID, DRV/r 800/100 mg QD, and two nucleoside reverse transcriptase inhibitors (NRTIs) for 4 weeks (Phase I); and DTG 50 mg QD with two NRTIs thereafter (Phase II: reference). Total DTG trough concentration (C trough) and area under the concentration–time profile of 0–24 h (AUC 0–24h) were predicted using a population PK model. DTG glucuronidation metabolic ratio (MR) and DTG free fraction were determined and compared per treatment phase using geometric mean ratio (GMR) and 90% confidence interval (CI). Participants had a predicted geometric mean steady-state DTG C trough of 2.83 [coefficient of variation (CV%) 30.3%] mg/L (Phase I) and 1.28 (CV% 52.4%) mg/L (Phase II), with GMR of 2.20 (90% CI 1.90–2.55). Total exposure during DTG BID increased but did not double [AUC 0–24h GMR 1.65 (90% CI 1.50–1.81) h.mg/L]. DTG glucuronidation MR increased by approximately 29% during Phase I. DTG C trough was above in-vivo EC 90 (0.32 mg/L) during both phases, except in one participant during Phase I. At Week 8, 84% of participants had viral loads ≤40 copies/mL. The drug–drug interaction between DTG (BID) and DRV/r (QD) was due to induced glucuronidation, and is not clinically relevant in patients with AHI. [ABSTRACT FROM AUTHOR]