BioEd Online

One by one, trials to see whether painkillers can cure big diseases such as cancer and Alzheimer's are being dismantled. It seems that a certain class of these drugs may increase your risk of heart attack or stroke.

The latest trial to be brought to a halt was run by the National Institutes of Health's National Institute on Aging. It was hoping to show that a daily dose of painkiller (either celecoxib, marketed by Pfizer as Celebrex, or naxopren, known as Aleve) could ward off the mental degeneration caused by Alzheimer's disease. The study will continue to observe participants, but it is unlikely that they will be given any more drugs.

Doses were stopped, ultimately, because of the patients' concerns about one of the drugs they were taking. Celecoxib is a 'cox-2 inhibitor' like rofecoxib, the drug that pharmaceutical giant Merck took off the market in September, following fears that it could increase risk of stroke.

After the withdrawal of rofecoxib, sold as Vioxx, some researchers suggested that the whole class of drugs might be dangerous, and participants in the Alzheimer's study got nervous. "We were having a devil of a time keeping people on the medicine," says John Breitner, a geriatric specialist at University of Washington in Seattle, who ran the trial.

Then, last week, the National Cancer Institute suspended a trial studying whether celecoxib might help prevent colorectal cancer. An advisory panel had pointed out that participants on celecoxib had a 2.5-fold increased risk of major heart problems compared with those taking a placebo.

When word got out, says Breitner, "we were doomed". No one would stay on the pills. He and his team spent the weekend calling patients and telling them to stop taking their daily doses.

However, Breitner's trial data show no increased heart risk for participants taking celecoxib, even after three years.

A new suspect?

Interestingly, Breitner's results show there was a roughly 50% increase in risk of heart problems for those taking the naproxen, which belongs to a class of painkiller that is sold over the counter and to which ibuprofen also belongs.

There are no trials of the long-term use of this type of painkiller, but Breitner's independent safety panel decided on 10 December that the naproxen risks were minor. It recommended that the study continue and it was actually the fears of the participants that made Beringer decide to pull the plug.

Public scrutiny

Elias Zerhouni, the director of the National Institutes of Health, acknowledged in a press conference on 20 December that "under normal circumstances, this probably would not have been raised to the level of a press briefing". But, he said, intense focus on the risks of painkillers made him feel that explaining why the drugs were dropped from the Breitner trial was necessary.

Zerhouni emphasized that pulling a drug from a trial, where the benefit to the participant is hypothetical, is very different from taking a drug off the market and away from people who manifestly do benefit from it. The US Food and Drug Administration (FDA) has recommended that people should keep taking naproxen and drugs like it. But it says that they should follow the directions on the bottle, which generally prohibit taking the pills for more than ten days in a row.

Sandy Kweder, deputy director of the FDA's Office of New Drugs, called the situation "very confusing". She said that the FDA would be looking at the results carefully, but that "we are not contemplating any specific regulatory actions in the next few days".