FDA strengthens Plavix safety warning

A boxed warning has been added to the US packaging of Sanofi-Aventis and Bristol-Myers Squibb’s blockbuster anti-clotting drug Plavix.

The US Food and Drug Administration (FDA) imposed the change, which explains the drug can be less effective in people whose bodies cannot convert the drug to its active form.

The information was in fact added to the label last May, but after looking at extra data the FDA decided it should be made more prominent.

“We want to highlight this warning to make sure health care professionals use the best information possible to treat their patients,” said Mary Ross Southworth, clinical analyst in the FDA’s Center for Drug Evaluation and Research.

Poor metabolisers are estimated to make up a small percentage of the US patient population, and the packaging makes clear that people should continue to take Plavix(clopidogrel) unless told not to by a specialist.

The brand reduces the risk of heart attack, unstable angina, stroke, and cardiovascular death in patients with cardiovascular disease by making platelets less likely to form blood clots.

But these anti-platelet effects are not apparent until it is metabolised into its active form by the liver enzyme, CYP2C19, and it may be less effective in people who have reduced functioning of CYP2C19.

This means those taking Plavix could remain at risk for heart attack, stroke and cardiovascular death.

The CYP2C19 genotype can be tested to see whether a patient is a poor metaboliser – and the prescribing information says this is likely to be the case with around 2% of white people, 4% of blacks and 14% of Chinese.

The FDA recommends that these patients should be considered for an alternative dose of Plavix or that other anti-platelet drugs should be used.

Plavix is contraindicated in patients with active pathological bleeding, such as peptic ulcer or intracranial hemorrhage, or with hypersensitivity, such as anaphylaxis, to clopidogrel.

The brand has been threatened by generic competition, particularly in Europe, and last year global sales dropped 10.4% to 1.51 billion euros.