Prilosec Side Effects Interfere with Effectiveness of Plavix: FDA Warns

The FDA has issued a public health advisory warning that side effects of Prilosec, a stomach acid reducer, may interfere with the effectiveness of Plavix, an anti-blood clotting medication, increasing the risk of a heart attack, death or other injuries for patients.

The advisory was released on November 17 after an FDA review of the effects of combining Prilosec and Plavix found that use of the drugs together reduces the effects of Plavix by about 50%. Therefore, the regulatory agency is requiring new warnings on the label for Plavix, Prilosec and other heartburn drugs that work the same way by inhibiting the CYP2C19 enzyme, which could interact with Plavix.

The announcement comes on the heels of a study presented at an annual meeting of the American Heart Association that found heart patients given medications known as proton pump inhibitors (PPIs), like Prilosec and Protonix, were more likely to die after heart surgery. The study, conducted by researchers at Mount Sinai Medical Center in New York, found that the risk of death for heart surgery patients on Prilosec was 30% higher than for other patients.

Plavix (clopidogrel) is a blood thinner that prevents blood platelets from sticking together to form clots. It is prescribed to prevent heart attacks, strokes and blood clotting when drug coated stents are used in patients with arteriosclerosis and in other at-risk patients. It is a blockbuster medication, generating annual sales of over $6 billion for Bristol Myers Squibb Co. and Sanofi-Aventis.

Prilosec (omeprazole) is a proton pump inhibitor used to reduce stomach acid, which is manufactured by AstraZeneca and available as a generic.

Prilosec and other stomach acid drugs are often prescribed along with Plavix, to combat upset stomachs caused by gastrointestinal bleeding, a common Plavix side effect. The FDA indicates that Prilosec may actually inhibit the drug metabolizing enzyme in the body that normally would convert Plavix into its active form, which reduces its effectiveness, putting patients at risk of heart attack and stroke.

The FDA began its review of the drug interactions in January. In March, a study published in the Journal of the American Medical Association found that patients were 25% more likely to be readmitted to the hospital or die if they were also taking a proton pump inhibitor with Plavix.

The FDA is warning health care professionals not to prescribe Plavix and Prilosec together, and is also warning patients not to take the over-the-counter version of Prilosec or similar drugs to fight upset stomachs that occur while on Plavix. The FDA also suspects that Nexium, also manufactured by AstraZeneca, will have the same reduction of Plavix effectiveness. Other drugs which may inhibit Plavix include Tagamet and Tagamet HB, Diflucan, Nizoral, VFEND, Intelence, Felbatol, Prozac, Serafem, Symbyax, Luvox and Ticlid.

The FDA recommends that patients who are taking Plavix can use antacids and acid-reducers known as H2 blockers to combat Plavix side effects. The agency believes that taking Zantac, Pepcid, Axid, Mylanta and Maalox are safe alternatives.