Public Citizen, which has successfully lobbied against certain diet pills and other drugs and which each year exposes doctors who have been disciplined by medical boards, said the study is using the wrong drugs.
The trial, called the Alzheimer's Disease Anti-Inflammatory Prevention Trial or ADAPT, has enrolled about 1,000 elderly people who have a relative with Alzheimer's or some other kind of dementia or memory loss.
Sponsored by the National Institute of Aging, the trial aims to give the volunteers either one of two analgesic drugs or a placebo, and see who goes on to develop Alzheimer's.
Alzheimer's affects an estimated 4 million Americans and the number is expected to rise as the baby boomer generation ages. The few drugs used to treat it do not work well and none work for long, so Alzheimer's remains incurable and invariably fatal.
Victims start out with vague memory loss but gradually lose the ability to care for themselves.
Studies have suggested that people who use analgesics called non-steroidal anti-inflammatory agents or NSAIDS, a class that includes aspirin and ibuprofen, may have a lower risk of Alzheimer's. The ADAPT study was designed to probe this.
Pharmacia and Bayer are providing the drugs being used in the study: celecoxib, sold under the brand name Celebrex, and naproxen, sold as Naprosyn.
Public Citizen contends that there is no reason to believe either drug will work. The group furthermore says the drugs - like all NSAIDS - can have serious and even deadly side effects. The worst side effect associated with NSAIDS in general is stomach bleeding, which kills thousands every year, according to Public Citizen.
"Because patients are taking drugs without true informed consent, Public Citizen urges the NIA to immediately stop this unethical trial and provide patients already enrolled in the trial with the information previously denied them on lack of plausible benefit as well as the possible health risks," the group wrote in a letter to Health and Human Services Secretary Tommy Thompson.
The group cites studies that show NSAIDS may work against Alzheimer's not because of their main mechanism of action - suppression of inflammation via the COX-2 enzyme - but because of their action on beta-secretase, another enzyme.
The group says the studies showing these effects used other NSAIDS - ibuprofen, indomethacin and sulindac.
The National Institute on Aging said it was preparing a response to the letter. A spokesman for HHS said the agency and all of the National Institutes of Health relied on scientific findings for their research.
"This is just one person's opinion on the subject," HHS spokesman Bill Pierce said. "The letter has been forwarded to the NIA."
Public Citizen alleges the trial is using Celebrex and Naprosyn only because the companies are supplying the drugs and not because of any evidence they will actually work.
By Maggie Fox