The calcium blocker nifedipine used to treat high blood pressure has been singled out by the US's Food and Drug Administration (FDA) for increasing the risk of heart attack in some patients.

The FDA's conclusion mirrors that of the National Institutes of Health, which pronounced five months earlier that short acting nifedipine should be used with great caution.

Nifedipine works by suddenly bringing down blood pressure, but it rises sharply in the five hours before the next dose. "I don't think that's a sensible way to treat high blood pressure," commented the FDA's Robert Temple.

It seems unlikely the FDA will go so far as to impose a ban, or even a warning, on the drug, but is likely instead to include more information about the drug when it's despatched to doctors.

As a family, however, the FDA has considered calcium channel blockers to be safe.

It will be interesting to see if the latest FDA pronouncement may spark a new wave of damage limitation activities by the drug manufacturers. After the NIH announcement last September, US doctors were sent a letter from "an internationally recognized expert in the treatment of hypertension", who suggested that the findings did not relate to nifedipine. It was printed on the writer's university stationery.

However, when one doctor investigated further, he discovered that the letter and campaign had been funded by Bayer Corp, one of the two makers of nifedipine in the US. He had been approached by a public relations company representing Bayer, and he had been asked to write a letter defending the drug. He had been assured that Bayer's name would appear on the letter and envelope, although this was "inadvertently left off," according to a Bayer spokesman.