Five prescription drugs currently are approved by the U.S. Food and Drug Administration to treat people who have been diagnosed with Alzheimer disease (AD). Treating the symptoms of AD can provide patients with comfort, dignity and independence for a longer period of time and can encourage and assist their caregivers as well.
It is important to understand that none of these medications stops the disease itself.
Treatment for Mild to Moderate AD
Four of these medications are called cholinesterase inhibitors. These drugs are prescribed for the treatment of mild to moderate AD. They may help delay or prevent symptoms from becoming worse for a limited time and may help control some behavioral symptoms. The medications are: Razadyne® (formerly known as Reminyl®) (galantamine), Exelon® (rivastigmine), Aricept® (donepezil) and Cognex® (tacrine). Scientists do not yet fully understand how cholinesterase inhibitors work to treat AD, but current research indicates that they prevent the breakdown of acetylcholine, a brain chemical believed to be important for memory and thinking. As AD 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 AD patient may respond better to one drug than another. Cognex® (tacrine) is no longer actively marketed by the manufacturer.
Treatment for Moderate to Severe AD
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 AD. Studies have shown that the main effect of Namenda® is to delay progression of some of the symptoms of moderate to severe AD. 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 AD 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.
The FDA also has approved Aricept® for the treatment of moderate to severe AD.
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.
Additional Resources
Alzheimer’s Association
225 N. Michigan Ave., Suite 1700
Chicago, IL 60601
1-800-272-3900
Internet: www.alz.org
Alzheimer’s Disease Education and Referral (ADEAR) Center
PO Box 8250
Silver Spring, MD 20907-8250
1-800-438-4380
Internet: https://www.nia.nih.gov/health/alzheimers
Table Medications to Treat Alzheimer Disease
| DRUG NAME | DRUG TYPE AND TREATMENT | MANUFACTURER’S RECOMMENDED DOSAGE |
| Namenda® (memantine)
Blocks the toxic effects associated with excess glutamate and regulates glutamate activation. |
N-methyl D-aspartate (NMDA) antagonist prescribed to treat symptoms of moderate to severe AD | 5 mg, once a day, available in tablet form
Increase to 10 mg/day (5 mg twice a day), 15 mg/day (5 mg and 10 mg as separate doses) and 20 mg/day (10 mg twice a day) at minimum of one-week intervals if well tolerated. |
| Razadyne® (formerly known as Reminyl®) (galantamine)
Prevents the breakdown of acetylcholine and stimulates nicotinic receptors to release more acetylcholine in the brain. |
Cholinesterase inhibitor prescribed to treat symptoms of mild to moderate AD | 4mg, twice a day (8mg/day, available in tablet or capsule form
Increase by 8mg/day after four weeks to 8mg, twice a day (16mg/day) if well tolerated. After another four weeks, increase to 12mg, twice a day (24mg/day) if well tolerated. |
| Exelon® (rivastigmine)
Prevents the breakdown of acetylcholine and butyrylcholine (a brain chemical similar to acetylcholine) in the brain. |
Cholinesterase inhibitor prescribed to treat symptoms of mild to moderate AD | 1.5mg, twice a day (3mg/day, available in capsule and liquid form
Increase by 3mg/day every two weeks to 6mg, twice a day (12mg/day) if well tolerated. |
| Aricept® (donepezil) Prevents the breakdown of acetylcholine in the brain. | Cholinesterase inhibitor prescribed to treat symptoms of mild to moderate, and moderate to severe AD | 5mg, once a day, available in tablet form
Increase after four to six weeks to 10mg, once a day if well tolerated. |
| Cognex® (tacrine)
Prevents the breakdown of acetylcholine in the brain. Note: Cognex is still available but no longer actively marketed by the manufacturer. |
Cholinesterase inhibitor prescribed to treat symptoms of mild to moderate AD | 10mg, four times a day (40mg/day), in capsule form
Increase by 40mg/day every four weeks to 40mg, four times a day (160mg/day), if liver enzyme functions remain normal and if well tolerated. |
| DRUG NAME | COMMON SIDE EFFECTS | POSSIBLE DRUG INTERACTIONS |
| Namenda® (memantine)
Blocks the toxic effects associated with excess glutamate and regulates glutamate activation. |
Dizziness, headache, constipation, confusion | Other NMDA antagonist medications, including amantadine, an antiviral used to treat the flu, dextromethorphan, prescribed to relieve coughs due to colds or flu, and ketamine, sometimes used as an anesthetic, have not been systematically evaluated and should be used with caution in combination with this medication. |
| Razadyne® (formerly known as Reminyl®) (galantamine)
Prevents the breakdown of acetylcholine and stimulates nicotinic receptors to release more acetylcholine in the brain. |
Nausea, vomiting, diarrhea, weight loss | Some antidepressants such as paroxetine, amitriptyline, fluoxetine, fluvoxamine and other drugs with anticholinergic action may cause retention of excess Razadyne® (formerly known as Reminyl®) in the body, leading to complications; NSAIDs should be used with caution in combination with this medication.* |
| Exelon® (rivastigmine)
Prevents the breakdown of acetylcholine and butyrylcholine (a brain chemical similar to acetylcholine) in the brain. |
Nausea, vomiting, weight loss, upset stomach, muscle weakness | None observed in laboratory studies; NSAIDs should be used with caution in combination with this medication.* |
| Aricept® (donepezil) Prevents the breakdown of acetylcholine in the brain. | Nausea, diarrhea, vomiting | None observed in laboratory studies; NSAIDs should be used with caution in combination with this medication.* |
| Cognex® (tacrine)
Prevents the breakdown of acetylcholine in the brain. Note: Cognex is still available but no longer actively marketed by the manufacturer. |
Nausea, diarrhea, possible liver damage | NSAIDs should be used with caution in combination with this medication.* |
* Use of cholinesterase inhibitors can increase risk of stomach ulcers, and because prolonged use of non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin or ibuprofen also can cause stomach ulcers, NSAIDs should be used with caution in combination with these medications.
Source: National Institute on Aging, National Institutes of Health
Updated: December 19, 2006
