Donepezil

Donepezil

Definition

Donepezil is a drug used to treat dementia associated with Alzheimer's disease . In the United States, donepezil is sold under the brand name Aricept.

Purpose

Donepezil is used to help treat symptoms of Alzheimer's disease in individuals with mild to moderate illness. The drug may cause small improvements in dementia for a short period of time, but donepezil does not stop the progression of Alzheimer's disease.

Description

The Food and Drug Administration has approved donepezil for treatment of the symptoms of Alzheimer's disease. In Alzheimer's disease, some cells in specific regions of the brain die. Because of this cell death, these brain cells lose their ability to transmit nerve impulses. Brain cells normally transmit nerve impulses by secreting various chemicals known as neurotransmitters .

Brain cells that make and secrete a neurotransmitter called acetylcholine are affected early in the course of Alzheimer's disease. Donepezil helps prevent the breakdown of acetylcholine in the brain, thus temporarily increasing its concentration. In doing so, donepezil may improve the thinking process by facilitating nerve impulse transmission within the brain.

Donepezil is available as tablets in two different strengths. It is broken down by the liver.

Recommended dosage

The initial dosage of donepezil is 5 mg taken at bedtime. This dose should be continued for four to six weeks. The dosage may then be increased to 10 mg at bedtime, but there is no clear evidence that the higher dosage is more beneficial. However, the higher dosage is likely to cause more side effects.

Precautions

Donepezil may slow heart rate, increase acid in the stomach, make urination difficult, cause breathing difficulties, and may make it more likely for people to have seizures . As a result, it should be used carefully with close physician supervision by people with certain heart conditions, those who are prone to stomach ulcers, people with bladder obstruction, individuals with asthma or chronic obstructive pulmonary disease, and people with a history of seizure disorders.

People taking donepezil should be reassessed periodically to determine whether the drug is providing any benefits. When caregivers feel the drug is no longer beneficial, it may be stopped.

Side effects

More than 5% of people taking donepezil experience difficulty sleeping, dizziness, nausea, diarrhea, muscle cramps, headache, or other pains.

Diarrhea, nausea, and vomiting occur more often with the 10-mg dose than the 5-mg dosage. These adverse effects are usually mild, short-lived, and typically subside when the drug is stopped. Other, less common, side effects are abnormal dreams, depression, drowsiness, fainting, loss of appetite, weight loss, frequent urination, arthritis, and easy bruising.

Interactions

Many drugs may alter the effects of donepezil; likewise, donepezil may alter the action of other drugs. Drugs such as dicylomine, phenytoin, carbamazepine , dexamethasone, rifampin, or phenobarbital may lessen the effects of donepezil. Other drugs such as bethanechol, ketoconazole, or quinidine may increase some of the side effects associated with donepezil. When donepezil and nonsteroidal anti-inflammatory drugs such as ibuprofen (Advil) or naproxen are used together, there may be an increased tendency to develop stomach ulcers. Donepezil may increase the side effects associated with use of fluvoxamine , an antidepressant. If succinylcholine, a drug commonly used during anesthesia, is used with donepezil, prolonged muscle paralysis may result.

Resources

BOOKS

Eisai Co. Staff. Aricept Package Insert. Tokyo, Japan: Eisai Co. Ltd, 2000.

Facts and Comparisons Staff. Drug Facts and Comparisons. 6th Edition. St. Louis: Facts and Comparisons, 2002.

Mosby Staff. Mosby's Medical Drug Reference. St. Louis, MO: Mosby, Inc, 1999.

Kelly Karpa, RPh, Ph.D.