Warning over atazanavir and Prilosec, other acid control drugs too

Keith Alcorn
Estimated reading time 2 minutes
This article is more than 20 years old.

Bristol-Meyers Squibb has issued a Dear Healthcare Provider letter warning doctors and patients not to combine Reyataz (atazanavir) and Norvir (ritonavir) with Prilosec (omeprazole). Omeprazole is a proton-pump inhibitor (PPI) for the treatment of acid-related diseases that works by suppressing gastric acid secretion. The company has also reminded patients to be cautious when dosing medicines such as cimetidine (Tagamet) and ranitidine (Zantac) with atazanavir until further research is carried out.

Bristol Myers Squibb reported yesterday that a randomised, multiple dose interaction study had revealed a 76% reduction in atazanavir area under the concentration-time curve (AUC) and a 78% reduction in atazanavir trough plasma concentration (Cmin) when Reyataz/ritonavir 300/100 mg was coadministered with omeprazole 40 mg. Simultaneous administration of 8 ounces of cola given in an effort to decrease (acidify) gastric pH did not appear to affect this reduction.

Increasing the Reyataz/ritonavir dose to 400/100 mg in combination with omeprazole did not result in Reyataz exposures comparable to those observed with a regimen of Reyataz/ritonavir 300/100 mg without omeprazole.

Glossary

receptor

In cell biology, a structure on the surface of a cell (or inside a cell) that selectively receives and binds to a specific substance. There are many receptors. CD4 T cells are called that way because they have a protein called CD4 on their surface. Before entering (infecting) a CD4 T cell (that will become a “host” cell), HIV binds to the CD4 receptor and its coreceptor. 

drug interaction

A risky combination of drugs, when drug A interferes with the functioning of drug B. Blood levels of the drug may be lowered or raised, potentially interfering with effectiveness or making side-effects worse. Also known as a drug-drug interaction.

concentration (of a drug)

The level of a drug in the blood or other body fluid or tissue.

plasma

The fluid portion of the blood.

proton-pump inhibitor

A drug for the treatment of heartburn and acid reflux, which works by blocking the enzyme system in the stomach that produces acid.

It is not known whether the over-the-counter dose of omeprazole (20 mg once daily) would produce similar results; therefore, coadministration is not recommended.

Investigations regarding the potential drug interaction between atazanavir and H2-Receptor antagonists (another type of gastric medication that includes the drugs ranitidine and cimetidine) when coadministered are ongoing. Until data are available, clinicians should note the following statements from the Reyataz Package Insert: "Reduced plasma concentrations of atazanavir are expected if H2-receptor antagonists are administered with Reyataz (atazanavir sulfate). This may result in loss of therapeutic effect and development of resistance. To lessen the effect of H2 -receptor antagonists on atazanavir exposure, it is recommended that an H2-receptor antagonist and Reyataz be administered as far apart as possible, preferably 12 hours apart."

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