In the Alzheimer's Series:

• An Introduction to Alzheimer's
• Symptoms of Alzheimer's
• Causes of Alzheimer's
• Treatment of Alzheimer's
• How Alzheimer's is Diagnosed
• What is the Outlook for Alzheimer's?
• Further Information

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.

Treatment for Mild to Moderate Alzheimer's disease

Four of these medications are called cholinesterase inhibitors. These drugs are prescribed for the treatment of mild to moderate Alzheimer's disease. They may help delay or prevent symptoms from becoming worse for a limited time and may help control some behavioral symptoms. The medications are: Reminyl® (galantamine), Exelon® (rivastigmine), Aricept® (donepezil), and Cognex® (tacrine). Scientists do not yet fully understand how cholinesterase inhibitors work to treat Alzheimer's disease, but current research indicates that they prevent the breakdown of acetylcholine, a brain chemical believed to be important for memory and thinking. As Alzheimer's disease progresses, the brain produces less and less acetylcholine; therefore, cholinesterase inhibitors may eventually lose their effect.

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.

Treatment for Moderate to Severe Alzheimer's disease

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.

Dosage and Side Effects

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.

Last reviewed:
  On 12 Oct 2006
  By John M. Grohol, Psy.D.