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Bristol-Meyers Squibb has issued a Dear Healthcare Provider letter regarding important new pharmacokinetic data concerning the coadministration of 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 following observations were made from a randomized, open-label, multiple-dose drug interaction study.

A 76% reduction in atazanavir area under the concentration-time curve (AUC) and a 78% reduction in atazanavir trough plasma concentration (C_min) were observed when REYATAZ/ritonavir 300/100 mg was coadministered with omeprazole 40 mg.

Based on the study results:

* DO NOT COADMINISTER REYATAZ OR REYATAZ/ritonavir with omeprazole due to the reduction in atazanavir exposure levels. This recommendation is consistent with the current REYATAZ U.S. Package Insert.
 

* 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.

* 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.

* Simultaneous administration of 8 ounces of cola given in an effort to decrease (acidify) gastric pH did not appear to affect this reduction.

Investigations regarding the potential drug interaction between REYATAZ (atazanavir sulfate) and H2-Receptor antagonists (another type of gastric medication) 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."

A copy of the complete letter is attached in pdf format.

To view or print the document, you can use the free Adobe Acrobat, available directly from Adobe's Website with full installation instructions. http://www.adobe.com/products/acrobat/readstep2.html

Richard Klein
Office of Special Health Issues
Food and Drug Administration

Kimberly Struble
Division of Antiviral Drug Products
Food and Drug Administration

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