Coadministration of Elvitegravir and Acid-Reducing Agents

Summary and Comment |
September 6, 2013

Coadministration of Elvitegravir and Acid-Reducing Agents

  1. Sonia Nagy Chimienti, MD

Staggered dosing is necessary for antacids but not for histamine-2–receptor antagonists or proton-pump inhibitors.

  1. Sonia Nagy Chimienti, MD

Acid-reducing agents — antacids, histamine-2–receptor antagonists, and proton-pump inhibitors — are commonly used in medical practice and may interact with antiretroviral medications. Investigators recently conducted a series of four clinical studies to evaluate the effects of acid-reducing agents on drug levels of boosted elvitegravir. Elvitegravir, a once-daily integrase inhibitor, is a component of the elvitegravir/cobicistat/FTC/tenofovir single-tablet regimen (Stribild).

The four studies were all manufacturer-sponsored, phase I, single-center, open-label, crossover trials, conducted in healthy adult volunteers:

  • Study 1 evaluated ritonavir-boosted elvitegravir, taken alone or simultaneously with an antacid.

  • Study 2 evaluated elvitegravir/r, taken with an antacid in a staggered fashion (±2 or ±4 hours) or with omeprazole (used 2 hours earlier).

  • Studies 3 and 4 evaluated cobicistat-boosted elvitegravir, taken alone or with famotidine or omeprazole (simultaneously or staggered by 12 hours).

Elvitegravir was taken immediately after a standardized, approximately 400-kcal morning meal.

Adverse effects occurred in up to 44% of participants in each of the studies and were generally mild; no serious events (grade 3 or 4) or deaths were reported. Study discontinuations were infrequent: none in studies 1 and 4, 10 of 60 in study 2 (tolerability in 4, protocol violation in 4, and withdrawn consent in 2), and 1 of 32 in study 3 (pregnancy).

When elvitegravir/r was taken simultaneously with antacids, elvitegravir levels were lowered by approximately 50%; similar effects were not seen when use of the drugs was staggered by at least 2 hours. Elvitegravir levels were not significantly affected when elvitegravir/cobicistat was taken together with omeprazole or famotidine, or in a staggered fashion (≥2 hours) with an antacid.


Overall, the medications were well tolerated when coadministered, and adverse effects were primarily mild or moderate. When an antacid is used together with an elvitegravir-containing regimen, the drugs should be taken at least 2 hours apart. If a histamine-2–receptor antagonist or a proton-pump inhibitor is used, such staggering is not necessary.

  • Disclosures for Sonia Nagy Chimienti, MD at time of publication Nothing to disclose


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