Donepezil

"Mum has Alzheimer's," chirrups an advertisement for the drug donepezil hydrochloride in the medical press, "but she knew I was calling today." Unfortunately that's about as good as it's going to get for the visiting daughter.

Although donepezil appears to improve the cognitive functions in patients with mild to moderately severe Alzheimer's disease, it was not able to improve day-to-day functioning or quality of life as measured by the standard tests when it was analyzed in a 12-week, double-blind, placebo-controlled study (Dementia 1996; 7: 293-303).

The Drugs and Therapeutics Bulletin takes the manufacturer, Eisai-Pfizer, to task for basing too many claims on one piece of research. "It is not acceptable to ask doctors to make decisions on the basis of the results of a single, clinically inconclusive trial," its report concludes (DTB, 1997; 10: 75-6).

The bulletin says it cannot recommend the drug to physicians because the benefits to patients are unclear.

A follow on study, which analyzed the longer-term effects of donepezil over a two-year period, has been published only as an abstract, a partial way of reporting that is unsatisfactory. A second trial of the drug, involving 450 patients, has also been published only as an abstract.

Standard dosage is 5 mg daily taken just before going to bed. The drug can be prescribed only by a specialist able to diagnose and treat Alzheimer's dementia.

Side effects include diarrhea, nausea and vomiting, muscle cramps, fatigue and insomnia, which are twice as common while on the drug compared to placebo.

At the moment, there is little to offer an Alzheimer's patient other than supportive care, so any therapy that can offer help is to be welcomed. Donepezil has yet to prove conclusively that it is offering that ray of hope.