Patient and Pharmaceutical Company Implications: Avoid Using Plavix with Prilosec/Prilosec OTC

As the general U.S. population continues to age, more individuals are taking two or more prescribed drugs with Over the Counter (OTC) drugs. Researchers are just beginning to study polypharmacy and its effects on drug efficacy.
On November 17^th, 2009, the FDA announced that patients should avoid using the stomach acid reducer Prilosec/Prilosec OTC (omeprazole) with the anti-clotting drug Plavix (clopidogrel).

New data suggest that when patients take both Prilosec and Plavix, Plavix's ability to block platelet aggregation (anti-clotting effect) may be reduced by about half.

Plavix is used to prevent blood clots that could lead to heart attacks or strokes in at-risk patients. Omeprazole, the active ingredient of Prilosec and Prilosec OTC, is a proton pump inhibitor (PPI) used to reduce the production of stomach acid and prevent stomach irritation.

Blood clots are a leading killer. According to the CDC, about 350,000 to 600,000 Americans have a clot or one that leads to a pulmonary embolism each year, and at least 100,000 people die as a result. The trouble with clots is that half the people who have them do not know it; they find out when they start having chest pains labored breathing, a rapid heart rate, and seek emergency medical attention.

Anti-clotting drugs are expected to bring in more than $10 billion in annual sales in 2009, according to Thomson Pharma estimates. It is prescribed as a preventive measure to those most prone to a clot, such as people who have had recent surgery, or ones that have had an artery blockage in the past, and need to be especially careful to avoid clotting.

Plavix does not work until it is converted to its active form with the help of the liver enzyme, CYP2C19. Prilosec blocks the CYP2C19 enzyme, thereby reducing the effectiveness of Plavix.

The results of new studies compared people who took Plavix and Prilosec together with people who took Plavix alone. A reduction in Plavix's anti-clotting effect was found in those individuals who took the combination. Similar results were seen regardless of whether the two drugs were taken at the same or different times of day.

It is unknown how other PPIs may interfere with Plavix. Other drugs that should not be used with Plavix because they may have a similar interaction with CYP2C19 include Nexium (esomeprazole), Tagamet and Tagamet HB (cimetidine), Diflucan (fluconazole), Nizoral (ketoconazole), VFEND (voriconazole), Intelence (etravirine), Felbatol (felbamate), Prozac, Serafem, Symbyax (fluoxetine), Luvox (fluvoxamine) and Ticlid (ticlopidine).

Patient Implications:
Patients who take Plavix and need to take a drug to reduce stomach acid should discuss their therapy with a health care professional.
Zantac (ranitidine), Pepcid (famotidine), Axid (nizatidine), and antacids do not inhibit the CYP2C19 enzyme and aren't expected to interfere with the anti-clotting activity of Plavix.
Bristol Myers' will continue conducting studies to explore this and other drug interactions. When the FDA has reviewed additional data, the agency will communicate any new recommendations or conclusions.

Pharmaceutical Company Financial Implications:
The top name in the anti-clot game is Bristol Myers' (NYSE: BMY) Plavix, with expected revenue of $9.5 billion in 2009, making it the No. 2 prescription drug in the U.S., second only to Lipitor. Plavix has about 86 percent market share. Therefore, with this recent FDA announcement, one can expect physicians to consider prescribing other anti-clotting drugs. However, given its' popularity, the pharmaceutical company may attempt to persuade patients and physicians that giving up on their heartburn drugs are a better option compared to switching to a different anti-clotting drug.