Since 1986, when a report in the New England Journal of Medicine cited promising results in 14 patients with Alzheimer's disease, the drug now known as tacrine has had a difficult career. The medication was billed as offering some improvement to patients with Alzheimer's -- although questions about the research procedures undermined early optimism. Then it was discovered that tacrine has the potential to cause liver damage, and prospects dimmed even further (see the HMS Health Letter, March 1987 and January 1988). Last March the United States Food and Drug Administration withheld its approval for marketing in this country. Yet research conducted in Europe has provided some limited support for a beneficial effect.
A relatively large investigation by British researchers, published in April, provides additional evidence that the drug has some benefit in doses that do not threaten permanent liver damage, but the real value remains to be assessed. Eighty-nine patients entered the study; 19 of them had to be withdrawn because of side effects, and five more had to stop for other reasons. The remainder went through a 13-week period receiving either tacrine or a placebo. Then, after a four-week wait, they were switched to the other regimen.
Tests showed that mental function had improved -- about equivalent to undoing the deterioration that would be observed over a period of six months to a year. Improvement was also noted in relatively simple tasks, but not in more complex ones. No change was reported in a scale known as "Activities of Daily Living," which depends on a caregiver's ratings. It is unclear whether this was because the criteria of the scale were too crude to pick up real changes, or because the changes were simply too minimal to produce much benefit in a real-life situation.
Tacrine (formerly tetrahydroaminoacridine, or THA) remains both promising and disappointing. There is no reason to believe it can do anything beyond slowing the progress of Alzheimer's disease. Whether the relief is sufficient to be noticeable in daily life, and worth the risk of side effects, remains to be determined. (Lancet, April 27, 1991, pp. 989-992.)
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