Biktarvy should not be co-administered simultaneously with magnesium/aluminium-containing antacids. Biktarvy should be administered at least 2 hours before, or with food 2 hours after antacids containing magnesium and/or aluminium. Administration of maximum strength antacid (80 mg aluminium hydroxide, 80 mg magnesium hydroxide, and 8 mg simethicone, per mL; 20 ml single dose) and bictegravir was studied in fasting conditions. Administration of the antacid 2 hours prior to bictegravir decreased bictegravir AUC and Cmax by 52% and 58%. There was no significant change in bictegravir AUC and Cmax when the antacid was administered 2 hours after bictegravir. Simultaneous administration of the antacid and bictegravir decreased bictegravir AUC and Cmax by 79% and 80%. Simultaneous administration of the antacid and bictegravir with food decreased bictegravir AUC and Cmax by 47% and 49%. Decreases in bictegravir were due to chelation with polyvalent cations.

Coadministration may decrease bictegravir concentrations. Biktarvy can be taken at least 2 hours before or 6 hours after taking antacids containing aluminium/magnesium. Routine administration of Biktarvy together with, or 2 hours after, antacids containing aluminium/magnesium is not recommended. Coadministration of maximum strength antacid (80 mg aluminum hydroxide, 80 mg magnesium hydroxide, and 8 mg simethicone, per ml; 20 ml single dose) simultaneous with bictegravir (50 mg single dose) decreased bictegravir Cmax and AUC by 80% and 79%. Coadministration of maximum strength antacid (20 ml single dose) 2 h after bictegravir (50 mg single dose) decreased bictegravir Cmax and AUC by 7% and 13%. Coadministration of maximum strength antacid (20 ml single dose) 2 h before bictegravir (50 mg single dose) decreased bictegravir Cmax and AUC by 58% and 52%. Coadministration of maximum strength antacid (20 ml single dose) simultaneous with bictegravir (50 mg single dose) and food decreased bictegravir Cmax and AUC by 49% and 47%.

Bictegravir/emtricitabine/tenofovir alafenamide (50/200/25 mg single dose) was administered to HIV-uninfected subjects (n=14) simultaneously or temporally separated, under fasted or fed conditions, with/without maximum strength antacid (aluminium hydroxide 1600 mg, magnesium hydroxide 1600 mg, simethicone160 mg, single dose). Simultaneous administration decreased bictegravir AUC by 79% in fasting conditions and by 47% in fed conditions. Bictegravir AUC decreased by 13% when bictegravir was administered 2 hours before antacids and by 52% when administered 2 hours after antacids (both in fasting conditions).