In clinical trials that lasted over two years, Johnson & Johnson (NYSE:JNJ) found that its daffodil-extract Alzheimer's treatment, Reminyl, had a higher death rate than a placebo. During a time when regulators and pharmaceutical companies are concerned with the side effects of widely used drugs like Merck's (NYSE:MRK) Vioxx and Pfizer's (NYSE:PFE) Celebrex, Johnson & Johnson took no chances and reported the results to health authorities.

Reminyl is in a class of drugs known as cholinesterase inhibitors, which increase levels of acetylcholine, a chemical that transmits nerve signals in the brain. Some public advocacy groups have railed against the use of Reminyl and other such drugs in its class, saying they have been shown to have minimal benefits and their safety after taking them longer than six months is unknown. Other drugs in this class include Exelon from Novartis (NYSE:NVS) and Aricept, which is sold by Pfizer and Eisai.

The Reminyl study involved about 2,000 people in 16 countries. It was hoped that the drug could be used to treat mild cognitive impairment in Alzheimer's patients. There is no cure for the illness, and even Aricept, the No. 1 prescribed treatment for such impairment, only offers improvement in the day-to-day living condition of patients.

Johnson & Johnson found that 15 people died taking Reminyl compared to five taking a placebo. A number of the deaths were from heart attacks and strokes, and it is not believed that the drug itself actually caused any of them. In fact, the incidence of death among the elderly population in the trial was low, and serious side effects were the same for patients taking the drug or a placebo.

Manufactured with British Shire Pharmaceuticals (NASDAQ:SHPGY), Reminyl is approved for use in 69 countries for treating mild to moderate conditions of Alzheimer's, but has not been approved for mild cognitive impairment. Johnson & Johnson said it will not apply for this use, though it still supports Reminyl for its approved use.

Shire's shares fell some 4% when the news was released, after hitting a 52-week high of $36.05. Johnson & Johnson was off only 1% or so. Although it earns about $200 million a year from sales of Reminyl, Johnson & Johnson is wise to forgo pushing further applications for its use. Pharmaceutical companies in general are under the gun after the failure of the COX-2 inhibitors, and associating Reminyl with them, even though it's a completely different animal, might cause greater loss of investor confidence.

At least for this particular treatment of Alzheimer's, the daffodils are better left in the garden.

Merck is a selection of the Motley Fool Income Investor newsletter.

Fool contributor Rich Duprey owns shares of Merck and Eisai, but does not own any of the other stocks mentioned in this article.