- What is donepezil, and how does it work (mechanism of action)?
- What brand names are available for donepezil?
- Is donepezil available as a generic drug?
- Do I need a prescription for donepezil?
- What are the uses for donepezil?
- What are the side effects of donepezil?
- What is the dosage for donepezil?
- Which drugs or supplements interact with donepezil?
- Is donepezil safe to take if I'm pregnant or breastfeeding?
- What else should I know about donepezil?
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 are the uses for donepezil?
What are the side effects of donepezil?
The most common side effects associated with donepezil are:
- generalized pain,
- 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.
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.
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