Four prescription drugs currently are approved by the U.S. Food and Drug Administration to treat the symptoms of mild to moderate Alzheimer’s disease (AD). These medications are called "cholinesterase inhibitors." Scientists do not yet fully understand how these medications work to treat AD, but current research suggests that each acts to prevent the breakdown of acetylcholine, a brain chemical believed to be important for memory and thinking. These medications can help delay or prevent symptoms from becoming worse for a limited time and may help control some behavioral symptoms. 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.
None of these medications stops the disease itself. As AD progresses, the brain produces less and less acetylcholine, and the medications may eventually lose their effect. No published study directly compares these drugs, and as 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.
Some additional differences among these medications are summarized in the table on the other side. The medications (listed from most recent to last as approved by the FDA) are:
(Note: Cognex is still available but is not actively marketed by the manufacturer.)
Benefits reported for these medications tend to occur at higher doses. However, the higher the dose, the more likely are side effects. Doctors usually start patients at low doses, and gradually increase the dosage based on how well a patient tolerates the drug. Patients may be drug-sensitive in other ways, and they should be monitored for unusual symptoms 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.
Note: The brief summary provided below does not include all information important for patient use and should not be used as a substitute for professional medical advice. Consult the prescribing doctor and read the package insert before using these or any other medications or supplements. Drugs are listed from most recent to last, as approved by the FDA.
Drug Name: Reminyl® (galantamine) prevents the breakdown of acetylcholine and stimulates nicotinic receptors to release more acetylcholine in the brain.
Manufacturer Recommended Dosage: 4mg, twice a day (8mg/day)
Increase by 8mg/day after 4 weeks to 8mg, twice a day (16mg/day).
After another 4 weeks, increase to 12mg, twice a day (24mg/day), if well tolerated.
Common Side Effects: Nausea, vomiting, diarrhea, weight loss
Possible Drug Interactions: Some antidepressants such as paroxetine, amitriptyline, fluoxetine, fluvoxamine, and other drugs with anticholinergic action may cause retention of excess Reminyl in the body, leading to complications; NSAIDs should be used with caution in combination with this medication.*
Drug Name: Exelon® (rivastigmine) Prevents the breakdown of acetylcholine and butyrylcholine (a brain chemical similar to acetylcholine) in the brain.
Manufacturer Recommended Dosage: 1.5mg, twice a day (3mg/day)
Increase by 3mg/day every 2 weeks to 6mg, twice a day (12mg/day).
Continue up to 6mg, twice a day (12mg/day), if well tolerated.
Common Side Effects: Nausea, vomiting, weight loss, upset stomach, muscle weakness
Possible Drug Interactions: None observed in laboratory studies, NSAIDs should be used with caution in combination with this medication.*
Drug Name: Aricept® (donepezil) Prevents the breakdown of acetylcholine in the brain.
Manufacturer Recommended Dosage: 5mg, once a day, increase after 4-6 weeks to 10mg, once a day.
Common Side Effects: Nausea, diarrhea, vomiting
Possible Drug Interactions: None observed in laboratory studies, but NSAIDs should be used with caution in combination with this medication.*
Drug Name: Cognex® (tacrine) Prevents the breakdown of acetylcholine in the body, not specific to the brain. Note: Cognex is still available but no longer actively marketed by the manufacturer.
Manufacturer Recommended Dosage: 10mg, four times a day (40mg/day)
Increase by 40mg/day every 4 weeks to 40mg, four times a day (160mg/day), if liver enzyme functions remain normal.
Common Side Effects: Nausea, diarrhea, possible liver damage
Possible Drug Interactions: 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 can also cause stomach ulcers, NSAIDS should be used with caution in combination with these medications.
Source: National Institutes of Health Alzheimer’s Disease Education and Referral Center. www.alzheimers.org