No pharmaceutical opinion available for this interaction.
Calcium (antacid) could bind (chelation) to elvitegravir and reduce its absorption .
Elvitegravir 3A4 and then UGT1A1/3; Cobicistat 3A4 (major) and 2D6 (minor)
Elvitegravir : 2C9 (moderate)
Cobicistat : 3A4 and 2D6 (potent), P-gp, MATE 1, BCRP, OATP1B1 and OATP1B3
Possible decrease of clinical efficacy.
The product monograph recommends to separate administration of elvitegravir and antacids by at least 2 hours.
Monitor for clinical efficacy.
H2 receptor antagonists or proton pump inhibitors.
Ref #2134 : When an aluminum and magnesium hydroxide 20 mL dose is given simultaneously with elvitegravir, elvitegravir AUC and Cmin decreased by 45% and 41%, respectively. While the antacid given 2 or 4 hours before elvitegravir or 2 or 4 hours after elvitegravir does not influence elvitegravir plasma concentration significantly.
See elvitegravir/cobicistat + aluminium/magnesium hydroxide.
See also elvitegravir/cobicistat + famotidine and elvitegravir/cobicistat + omeprazole.