Donepezil is an oral medication used to treat Alzheimers disease. It belongs to a class of drugs called cholinesterase inhibitors that also includes tacrine Cognex. Scientists believe that Alzheimers 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 down the progression of Alzheimers disease. Donepezil was approved by the FDA in 1996.

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.

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 Alzheimers disease is associated with liver toxicity. Donepezil does not appear to be associated with liver toxicity.

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.

Donepezil is used for the treatment of mild to moderate dementia of the Alzheimers type.

Tablets should be stored at room temperature 15-30°C 59-86°F.