On the basis of new study results, FDA recommends the avoidance of combination use of proton pump inhibitor (PPI) omeprazole, used to reduce stomach acid, and clopidogrel (Plavix)used to prevent clotting of blood. The reason is that omeprazole reduces the anti-blood clotting effect of clopidogrel by almost half.The new recommendations are based on study results from the manufacturers of clopidogrel.

    It is evident through the studies that Omeprazole restricts the effect of the drug-metabolising enzyme (CYP 2C19), which is responsible for the conversion of clopidogrel into its active metabolite. The new studies compared the amount of clopidogrel’s active metabolite in the blood and its effect on platelets in patients who took clopidogrel plus omeprazole versus those who took clopidogrel alone. A reduction in active metabolite levels of about 45% was found in those who received clopidogrel with omeprazole compared with those taking clopidogrel alone.

    The effect of clopidogrel on platelets was reduced by as much as 47% in patients receiving clopidogrel and omeprazole together. It is to be noted that these reductions were seen whether the drugs were given at the same time or even 12 hours apart.
At this time, FDA does not have enough information about drug interactions between clopidogrel and PPIs other than omeprazole and esomeprazole to advise on their use together.