Date of report 08 Oct 2026

Reported case interaction between
Bictegravir and Antacids

A 41-year-old man with HIV infection had maintained virological suppression on bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF) for more than 2 years, with HIV-1 RNA consistently <30 copies/mL and no history of virological failure.

In March 2026, he developed persistent dyspeptic symptoms and independently started an over-the-counter antacid containing aluminium hydroxide, magnesium hydroxide and simethicone. He routinely took the antacid together with BIC/FTC/TAF in the morning before breakfast.

Six weeks later, routine laboratory monitoring showed an unexpected increase in HIV-1 RNA to 380 copies/mL. The patient reported complete adherence to ART and denied missed doses. Medication reconciliation identified the recently initiated antacid and its simultaneous administration with ART under fasting conditions.

Polyvalent cations such as aluminum and magnesium can chelate bictegravir in the gastrointestinal tract, substantially reducing its absorption. Simultaneous administration of an aluminum/magnesium containing antacid with bictegravir under fasting conditions has been shown to reduce bictegravir exposure by approximately 80%.

The antacid was therefore discontinued and replaced with famotidine 20 mg twice daily, for which no clinically significant interaction with BIC/FTC/TAF was expected. BIC/FTC/TAF was continued unchanged.

Four weeks later, HIV-1 RNA had returned to <30 copies/mL and remained suppressed during subsequent follow-up. No resistance-associated mutations were detected.

In this case, the temporal association between initiation of an aluminum/magnesium containing antacid, transient viraemia, and subsequent resuppression after antacid withdrawal is consistent with a clinically relevant drug-drug interaction, although causality cannot be established definitively.

The case also highlights the importance of explicitly asking about over-the-counter medications and supplements during medication reconciliation, as patients may not report these products spontaneously.

Aluminum and magnesium containing antacids should be appropriately separated from BIC/FTC/TAF according to prescribing recommendations. Alternatively, an acid-suppressive agent without polyvalent cations, such as an H2-receptor antagonist, may be used when clinically appropriate.