What is donepezil, and how does it work (mechanism of action)?
Donepezil is an oral medication used to treat
Alzheimer’s disease. It belongs to a class of drugs called cholinesterase
inhibitors that also includes tacrine (Cognex). Scientists believe that
Alzheimer’s disease may result from a deficiency in chemicals
(neurotransmitters) used by nerves in the brain to communicate with one another.
Donepezil inhibits acetylcholinesterase, an enzyme responsible for the
destruction of one neurotransmitter, acetylcholine. This leads to increased
concentrations of acetylcholine in the brain, and the increased concentrations
are believed to be responsible for the improvement seen during treatment with
donepezil. Donepezil improves the symptoms but does not slow the progression of
Alzheimer’s disease. Donepezil was approved by the FDA in 1996.
What brand names are available for donepezil?
Aricept, Aricept ODT
Is donepezil available as a generic drug?
Yes
Do I need a prescription for donepezil?
Yes
What are the uses for donepezil?
Donepezil is used for the treatment of mild, moderate, or
severe dementia associated with Alzheimer’s disease.
What are the side effects of donepezil?
The most common side effects associated with donepezil are:
- headache,
- generalized pain,
- fatigue,
- dizziness,
- nausea,
- vomiting,
- diarrhea,
- loss of appetite,
- weight loss,
- muscle cramping,
- joint pain,
- insomnia, and
- increased frequency of urination.
Other important side effects include:
What is the dosage for donepezil?
Donepezil is generally taken once daily at night prior to retiring.
Its absorption is not affected by food so that it may be taken with or without
food. Mild to moderate disease is treated with 5 or 10 mg once daily. Moderate
to severe Alzheimer’s disease is treated with 10 or 23 mg daily.
Which drugs or supplements interact with donepezil?
Drugs with anti-cholinergic properties that can cross into
the brain, such as atropine, benztropine (Cogentin), and trihexyphenidyl (Artane)
counteract the effects of donepezil and should be avoided during therapy with
donepezil.
Donepezil is metabolized (eliminated) by enzymes in the liver. The rate of
metabolism of donepezil may be increased by medications that increase the
amounts of these enzymes, such as carbamazepine (Tegretol), dexamethasone (Decadron),
phenobarbital, phenytoin (Dilantin), and rifampin (Rifadin). By increasing
elimination, these drugs may reduce the effects of donepezil.
Ketoconazole (Nizoral) has been shown to block the enzymes in the liver that
metabolize donepezil. Therefore, concurrent use of ketoconazole and donepezil
may result in increased concentrations of donepezil in the body and possibly
lead to donepezil side effects. Quinidine (Quinidex, Quinaglute) also has been
shown to inhibit the enzymes that metabolize donepezil and may cause donepezil
side effects.
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Is donepezil safe to take if I’m pregnant or breastfeeding?
It is not known whether donepezil is harmful to the fetus. Safe
use during pregnancy has not been established.
It is not known whether the donepezil is secreted into
breast milk or if breastfeeding while taking donepezil is safe for the nursing
infant.
What else should I know about donepezil?
What preparations of donepezil are available?
Tablets: 5, 10 and 23 mg. Tablets (orally disintegrating
tablets): 5 and 10 mg.
How should I keep donepezil stored?
Tablets should be stored at room temperature, 15-30 C (59-86 F).