The popular heartburn drugs Prilosec and Nexium can reduce by nearly half the blood thinning effect of the drug Plavix, said officials with the U.S. Food and Drug Administration (FDA) on Tuesday.
Plavix, known generically as clopidogrel, is an anti-clotting drug taken by millions of Americans to reduce risks of heart attack and stroke.
Nexium and Prilosec belong to a class of heartburn medications known as proton pump inhibitors (PPIs).
Regulators said the key ingredient PPIs blocks an enzyme the body needs to break down Plavix, and reduces the overall effect of the drug.
Procter & Gamble’s Prilosec (omeprazole) is the over-the-counter version of AstraZeneca’s Nexium (esomeprazole), which was approved in 2001.
“Patients at risk for heart attacks or strokes who use clopidogrel to prevent blood clots will not get the full effect of this medicine if they are also taking omeprazole,” said the FDA in a statement.
“A reduction in active metabolite levels of about 45% was found in people who received clopidogrel with omeprazole compared to those taking clopidogrel alone,” the agency said.
“The effect of clopidogrel on platelets was reduced by as much as 47% in people receiving clopidogrel and omeprazole together. These reductions were seen whether the drugs were given at the same time or 12 hours apart.”
Plavix, marketed by Sanofi-Aventis and Bristol-Myers Squibb, had worldwide sales $8.6 billion last year, and is the second-best selling drug after Pfizer’s cholesterol drug Lipitor.
But Plavix can sometimes cause an upset stomach, and is frequently prescribed with stomach acid-blocking drugs.
The FDA recommends that patients who need to reduce their stomach acid should take so called H-2 blockers such as Mylanta and Zantac, which show no evidence of interfering with Plavix’s blood clotting properties.
Although Nexium and Prilosec are both PPIs, FDA regulators said they do not have enough information to determine whether other PPIs should be avoided with Plavix.
“There’s not enough data to tell us how those drugs interact with,” the enzyme that activates Plavix, said the FDA’s deputy director for safety of cardiovascular products Mary Ross Southworth.
“There are ongoing studies looking at those other drugs.”
The FDA’s latest warning about drug interactions between Plavix and some heartburn medications is not new. Last year, researchers said that people taking Plavix with Nexium significantly increased their chances of being hospitalized for a heart attack, stroke or chest pain.
Sanofi and Bristol-Myers updated Plavix’s labeling in January to advise against using the drug in combination with certain heartburn medications.
The Associated Press quoted Sanofi spokeswoman as saying on Tuesday that the company has strengthened the language on its labels.
“We’ve strengthened the label to say that these drugs should be avoided altogether, not just discouraged,” said Sanofi senior communications director Noelle Boyd.