Many physicians still prescribe controversial drug combination

Safety concerns of the concomitant use of clopidogrel with the proton pump inhibitors (PPIs) omeprazole or esomeprazole were published in May 2009 and February 2010 by European regulatory agencies. After the last publication, there was an observed drop in dispensing these medicines in the Netherlands: 11.9 percent decreases for omeprazole and esomeprazole, versus an increase of 16.0 percent for other PPIs. Still 22.6 percent of patients started on omeprazole and esomeprazole in February 2010, placing them at risk for cardiovascular events.

Clopidogrel is an antiplatelet agent used to inhibit blood clots. Because of an increased risk of gastrointestinal bleeding with antiplatelet therapy, a PPI is often also prescribed, which reduces the secretion of stomach acid. Concomitant use of clopidogrel with esomeprazole/omeprazole may reduce the pharmacological activity of clopidogrel, however.

The study's findings indicate that advice from regulatory authorities were followed, but only reluctantly and not fully, probably partly because of scientific doubt about the interaction.

"Regulatory agencies should base their advice on sound scientific data to convince prescribers," said Willemien J. Kruik-Kolloffel, MSc, PharmD, lead author of the Pharmacology Research & Perspectives analysis. "We, the authors, doubt the interaction, as do a lot of professionals all around the world."