The Alzheimer's drugs Aricept, Razadyne and Exelon can lead to small improvements in mental functioning and the ability to carry out everyday activities in people with mild to moderate forms of the disease, according to a new review of recent studies.
Although the three drugs work in slightly different ways, the few head-to-head studies of the drugs -- all funded by pharmaceutical companies -- found them equally effective, according to review author Jacqueline Birks of the University of Oxford.
The review appears in the January issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.
Birks' review included 13 high-quality studies involving 7,298 patients from North America, Europe and Australia. The studies compared the three drugs against placebo treatment, with 2,228 patients in the Aricept studies, 2,267 in the Razadyne studies and 2,803 in the Exelon studies.
The effects of the drugs were not very large when measured across the 13 studies, Birks found. In one measure of how well the drugs worked, for instance, patients across the studies improved by an average of less than three points on a 70-point scale that tracks mental functioning.
"There is nothing to suggest the effects are less for patients with severe dementia, although there is very little evidence for other than mild to moderate dementia," she said.
Side effects caused about 29 percent of the patients taking the drugs to leave the studies, compared with 18 percent dropout among the patients taking a placebo. The most common side effects were nausea, vomiting and diarrhea.
Birks found fewer reported side effects among patients taking Aricept, but she suggests that this may have to do with the way Aricept and the other two drugs are prescribed.
Razadyne and Exelon have a "ramp-up" period in which patients take increasingly higher doses to get to a therapeutic level of treatment. Birks says the two drugs may be as tolerable as Aricept if they are gradually introduced over a course of three months.
In a second review focusing on Aricept only, Birks and researcher Richard Harvey found that a 5 milligram a day dose of the drug was only slightly less effective than a 10 milligram a day dose, with fewer side effects.
In another, newly updated Cochrane review, Dr. Clement Loy of Garvan Institute of Medical Research in Australia and colleagues concluded that Razadyne can improve or maintain mental functioning at a 16 milligram a day dose.