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DTG-Metformin Interaction — SCE Infectious Diseases MCQ

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ModerateHIV MedicineDTG-Metformin InteractionSCE Infectious Diseases

A 38-year-old man with HIV (CD4 520, VL <50 on DTG/TAF/FTC) develops new-onset diabetes mellitus. His HbA1c is 58 mmol/mol. His GP starts Metformin. What interaction exists between Dolutegravir and Metformin?

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Correct answer: B — DTG inhibits OCT2 and MATE1 transporters, increasing Metformin levels by ~80% — the Metformin dose should not exceed 1 g daily when co-administered with DTG

Dolutegravir inhibits renal organic cation transporter 2 (OCT2) and MATE1, which are responsible for Metformin renal secretion. This increases Metformin plasma levels by approximately 80%, raising the risk of lactic acidosis — particularly in patients with renal impairment. BHIVA and the BNF recommend limiting the Metformin dose to 1000 mg daily (500 mg BD) when co-administered with DTG. This interaction also applies to Bictegravir. Renal function should be monitored more closely.

Reference: BHIVA 2025 – ART guidelines; BNF 2024 – Dolutegravir-Metformin; Liverpool Drug Interactions