About
Donepezil
(doe NEP e zil)
Donepezil (Sold in the US as Aricept), is a centrally acting reversible acetylcholinesterase inhibitor. Its main therapeutic use is in the treatment of Alzheimer’s disease where it is used to increase cortical acetylcholine. It has an oral bioavailability of 100% and easily crosses the blood-brain barrier. Because it has a half life of about 70 hours, it can be taken once a day. Initial dose is 5 mg per day, which can be increased to 10 mg per day after an adjustment period of at least 4 weeks.
Preparations
Aricept is available in 5 and 10 mg tablets. Aricept ODT (orally disintegrating tablets) also are available in 5 and 10 mg tablets.
Storage
Tablets should be stored at room temperature, 15-30°C (59-86°F).
Prescribed For
Donepezil is used for the treatment of mild to moderate dementia of the Alzheimer’s type.
Dosing
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.
Drug Interactions
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.
Pregnancy
It is not known whether donepezil is harmful to the fetus. Safe use during pregnancy has not been established.
Nursing Mothers
It is not known whether the donepezil is secreted into breast milk or if breast-feeding while taking donepezil is safe for the nursing infant.
Side Effects
The most frequently reported side effects associated with donepezil include headache, generalized pain, fatigue, dizziness, nausea, vomiting, diarrhea, loss of appetite, weight loss, muscle cramping, joint pain, insomnia, and increased frequency of urination.
Tacrine (Cognex), another anticholinesterase medication used in the treatment of Alzheimer’s disease, is associated with liver toxicity. Donepezil does not appear to be associated with liver toxicity.
