In the Alzheimer's Series:
There is no cure for Alzheimer's disease and no way to slow the progression of the disease. For some people in the early or middle stages of Alzheimer's disease, medication such as tacrine (Cognex) may alleviate some cognitive symptoms. Donepezil (Aricept), rivastigmine (Exelon), and galantamine (Reminyl) may keep some symptoms from becoming worse for a limited time. A fifth drug, memantine (Namenda), was recently approved for use in the United States. Combining memantine with other Alzheimer's disease drugs may be more effective than any single therapy. One controlled clinical trial found that patients receiving donepezil plus memantine had better cognition and other functions than patients receiving donepezil alone. Also, other medications may help control behavioral symptoms such as sleeplessness, agitation, wandering, anxiety, and depression.
Alzheimer's disease is a progressive disease, but its course can vary from 5 to 20 years. The most common cause of death in Alzheimer's patients is infection.
No published study directly compares these drugs. Because all four work in a similar way, it is not expected that switching from one of these drugs to another will produce significantly different results. However, an Alzheimer's disease patient may respond better to one drug than another. Cognex® (tacrine) is no longer actively marketed by the manufacturer.
The fifth approved medication, known as Namenda® (memantine), is an N-methyl D-aspartate (NMDA) antagonist. It is prescribed for the treatment of moderate to severe Alzheimer's disease. Studies have shown that the main effect of Namenda® is to delay progression of some of the symptoms of moderate to severe Alzheimer's disease. The medication may allow patients to maintain certain daily functions a little longer. For example, Namenda® may help a patient in the later stages of Alzheimer's disease maintain his or her ability to go to the bathroom independently for several more months, a benefit for both patients and caregivers.
Namenda® is believed to work by regulating glutamate, another important brain chemical that, when produced in excessive amounts, may lead to brain cell death. Because NMDA antagonists work very differently from cholinesterase inhibitors, the two types of drugs can be prescribed in combination.
Doctors usually start patients at low drug doses and gradually increase the dosage based on how well a patient tolerates the drug. There is some evidence that certain patients may benefit from higher doses of the cholinesterase inhibitor medications. However, the higher the dose, the more likely are side effects. The recommended effective dosage of Namenda® is 20 mg/day after the patient has successfully tolerated lower doses. Some additional differences among these medications are summarized in the table on the other side.
Patients may be drug sensitive in other ways, and they should be monitored when a drug is started. Report any unusual symptoms to the prescribing doctor right away. It is important to follow the doctor's instructions when taking any medication, including vitamins and herbal supplements. Also, let the doctor know before adding or changing any medications.
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Last reviewed: By John M. Grohol, Psy.D. on 26 May 2013
Published on PsychCentral.com. All rights reserved.