Aricept, Exelon, Reminyl, and Namenda are approved to treat Alzheimer’s disease, but how well do they work?
Many patients and their caregivers have high expectations for drugs that are approved for treating Alzheimer’s disease. In certain instances, these expectations are met. For example, some Alzheimer’s disease patients experience improved memory and thinking, and some see benefits for up to five years with cholinesterase inhibitors. However, for the vast majority of people with Alzheimer’s disease, the effects of medication on cognition and behavior are much more modest.
Who Can Benefit?
The U.S. Food and Drug Administration (FDA) has approved five medications for the treatment of Alzheimer’s disease. Four of these are cholinesterase inhibitors—Cognex (tacrine), Aricept (donepezil), Exelon (rivastigmine), and Razadyne (galantamine)—which are approved to treat mild to moderate Alzheimer’s disease (a score of 10 to 26 on the Mini-Mental State Examination). Doctors rarely prescribe tacrine because it can cause serious liver problems.
Some studies show that cholinesterase inhibitors may benefit patients with severe Alzheimer’s disease, although the FDA has not approved them for this use. However, in October 2003 a new medication, Namenda (memantine), received FDA approval for the treatment of moderate to severe Alzheimer’s disease—that is, a score of less than 15 on the Mini-Mental State Examination. This drug is an NMDA receptor antagonist, not a cholinesterase inhibitor, and the two drug classes may have somewhat different effects.
Cholinesterase inhibitors are being investigated in patients with mild cognitive impairment. (No therapy has yet been shown to prevent the development of Alzheimer’s disease in people with this condition.) Researchers are also testing Namenda for mild to moderate Alzheimer’s disease.
What Are the Benefits?
Alzheimer’s disease drugs may be helpful in the following two areas:
- Cognition. Cholinesterase inhibitors improve cognition (memory, thinking, and language) in about two thirds of people with Alzheimer’s disease and may slow cognitive decline in some. If a patient does improve, the amount of improvement over one year is roughly equal to the amount of decline typically observed in untreated people with Alzheimer’s disease over 8 to 12 months. Yet a small number of patients continue to benefit from these drugs well beyond this time.
Because Namenda is a much newer drug, not as much information is available about its long-term cognitive effects. However, one 28-week study comparing Namenda with a placebo found that Namenda was associated with significantly decreased cognitive decline. Also, about 20% of patients taking Namenda had some improvement in cognition by the study’s end. Another study found that patients taking Namenda plus Aricept averaged less cognitive decline over 24 weeks than those taking a placebo plus Aricept, and about 40% of people taking Namenda plus Aricept experienced cognitive improvements.
- Daily function and behavior. Cholinesterase inhibitors and Nameda also can help with deficits in daily functioning and behavior that are prevalent in people with Alzheimer’s disease. Even small improvements in daily functioning and behavior are important because these problems are major reasons why caregivers end up placing Alzheimer’s disease patients in nursing homes. According to a review of 29 studies, patients with mild to moderate Alzheimer’s disease who took cholinesterase inhibitors experienced modest benefits in daily functioning (for example, dressing, bathing, and grooming) and modest improvements in behavioral problems (like hallucinations, agitation, paranoia, and depression). The review appeared in January 2003 in the Journal of the American Medical Association.
The two previously mentioned Namenda studies also demonstrated that the drug slows declines in daily functioning significantly more than a placebo. Also, about 20% of patients treated with Namemda alone and about 30% treated with Namenda plus Aricept experienced improvement in daily functioning.
Assessing Improvement
Patients taking Alzheimer’s disease drugs may not display obvious improvements in cognition, daily functioning, and behavior during the first few weeks of treatment. In fact, benefit may not become fully apparent for several months. Also, cholinesterase inhibitors may possibly help in one problem area—for example, behavior—while not affecting another aspect of the condition, like cognition.
Because all medications carry risks, patients should not remain on Alzheimer’s disease drugs if they do not benefit from them. Benefit can be determined in a number of ways: The person’s doctor may notice improvements during an examination; the caregiver may report improvements in areas like memory, communication, mood, daily functioning, or behavior; or the patient may perform better on a standardized test of mental function.
Because Namenda became available in 2004, practice patterns are still developing. However, in Europe, where cholinesterase inhibitors and Namenda have been available for longer, the two drugs are often prescribed together early in the disease. If the patient experiences no intolerable side effects from the medication, the physician will likely reassess the medication’s effectiveness roughly three months later and, from then on, about every six months. (If a patient cannot tolerate or doesn’t benefit from one cholinesterase inhibitor, it is often worthwhile to try another one.) If no medication improves the condition but the person is still in relatively good health, you may want to consider entering the person in a clinical trial.
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Posted in Memory on April 12, 2006
Reviewed June 2008
