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Tacrine: reversal of fortune?

In November 1986, California psychiatrist William K. Summers reported that 12 people with Alzheimer's disease had improved dramatically after taking an experimental drug now know as tacrine (SN: 11/15/86, p.308). These results, including the report that one Alzheimer's patient had resumed playing golf and another had gone back to work, spurred a number of clinical trials designed to test the drug's efficacy.

Since that time, researchers have reported mixed results on tacrine's efficacy and raised concern about liver damage (SN: 3/23/91, p.180).

Now, two new studies add to the growing file on tacrine. They both indicate that this experimental drug does provide benefits to some people with Alzheimer's disease, but the improvements appear modest.

A study in the Nov. 11 JOURNAL OF THE AMERICAN MEDICAL ASSOCIATION (JAMA) suggests that some people with Alzheimer's disease who took tacrine showed significant improvements on tests of memory and intellectual ability. Although there were no dramatic turn-arounds, some study participants were able to recognize family members after taking the drug, notes lead researcher Martin Farlow at the Indiana University Medical Center in Indianapolis.

Farlow and his colleagues at 21 U.S. and two Canadian medical centers began their study by recruiting 468 people with mild to moderate Alzheimer's symptoms. The researchers gave patients one of several different doses of tacrine capsules or a placebo. Neither the investigators nor the patients knew which patients received the drug and which got the inactive pills.

After 12 weeks of treatment, the people receiving tacrine showed a statistically significant improvement in the Alzheimer's Disease Assessment Scale, a test designed to measure memory and cognitive abilities. People who received the highest dose of tacrine (80 milligrams per day) showed the greatest improvement on this test, a finding which indicates that response to treatment increases with higher doses, Farlow says.

In addition, tacrine-treated patients exhibited improvement in the Clinical Global Impression of Change, a subjective scale completed by both doctors and family members. This scale helps the researchers gauge any overall change in a patient's ability to function, Farlow says.

About 25 percent of patients taking tacrine developed asymptomatic elevations in liver enzymes circulating in the bloodstream. These enzymes can be an early warning of liver damage, but the problem, disappeared when patients stopped taking tacrine, Farlow says. Side effects associated with the drug included nausea, vomiting, diarrhea, and rash.

The second study -- presented in part at a U.S. Food and Drug Administration advisory panel meeting last year (SN: 3/23/91, p.180)- shows marginal improvements as a result of tacrine treatment. Kenneth L. Davis of the Mount Sinai Medical Center in New York City and his colleagues studied 215 people with probable Alzheimer's disease who had mild to moderate impairments in memory and cognitive abilities. About half the group received varying doses of tacrine, while the remainder got a placebo. After six weeks, the team discovered that patients getting a tacrine treatment held their own in tests of cognitive ability, while those on placebo got progressively worse. Yet the investigators could detect no across-the-board improvement in people receiving tacrine, says researcher Lon S. Schneider of the University of Southern California in Los Angeles.

Taken together, the two studies add evidence to the belief that tacrine does provide relief, albeit modest, to victims of Alzheimer's disease, comments Gary W. Small at the University of California, Los Angeles. Small believes that Alzheimer's disease has more than one cause. Therefore, tacrine may benefit just a subset of patients, he says in an editorial that appears in the Nov. 11 JAMA.

Alzheimer's disease results in the death of brain cells known to make acetylcholine, a crucial neurotransmitter. Tacrine works by inhibiting an enzyme that breaks down acetylcholine, thus increasing the amount of this neuro-transmitter that lingers in brain tissue, Small says.

Officials at the Warner-Lambert Co., which manufacturers tacrine, remain confident of the drug's ability to clear the remaining regulatory hurdles at the FDA. The agency has yet to approve tacrine, but it has allowed people with Alzheimer's disease to obtain the drug through a limited program, Small says.
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Title Annotation:users of the drug may suffer side effects
Author:Fackelmann, Kathy A.
Publication:Science News
Date:Dec 5, 1992
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