Donepezil: 7 things you should know
Medically reviewed by Carmen Fookes, BPharm. Last updated on Nov 22, 2019.
1. How it works
- Donepezil may be used for the treatment of Alzheimer's Disease (AD).
- Donepezil enhances the effects of acetylcholine (a neurotransmitter) by blocking an enzyme responsible for its breakdown. Deficits in acetylcholine are thought to affect cognition and behavior, and impair everyday functioning and contribute to the symptoms of AD.
- Donepezil belongs to the group of medicines known as cholinesterase inhibitors.
- Donepezil may be used to treat mild, moderate, and severe Alzheimer’s disease (AD).
- Generic donepezil is available, which has increased the affordability of this treatment for people with AD.
If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:
- Diarrhea, nausea, and vomiting are common; prevalence increases with higher dosages and may be higher in those of a lower weight. Symptoms are usually transient and most resolve after one to three weeks of continued treatment. Muscle cramps and fatigue are also common.
- May increase gastric acid secretion and increase the risk of gastrointestinal bleeding and stomach ulcers. The risk is enhanced in people on concomitant non-steroidal anti-inflammatory drugs (NSAIDs).
- May cause weight loss at higher dosages, and there is a potential to inhibit urine flow or induce seizures.
- May not be suitable for people with certain heart conditions, a history of seizures, stomach ulcers, with difficulty passing urine, or lung conditions such as asthma or COPD.
- Caution is needed in people taking donepezil who require anesthesia. Discuss with an anesthetist.
- May interact with a number of other drugs including aspirin, those metabolized through CYP2D6, and anticholinergics (such as dicyclomine, scopolamine).
- Donepezil is not a cure for AD and some people do not respond as well as others.
Notes: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. For a complete list of all side effects, click here.
- Should be taken once daily in the evening, just prior to going to bed. Can be taken with or without food.
- Take donepezil exactly as directed by your doctor. Do not take more than recommended. Do not share your donepezil with other people as it may harm them. If you forget to take a tablet, do not double up on a dose, just take only the next dose at the usual time.
- Donepezil orally disintegrating tablets (ODT) should be allowed to dissolve slowly on the tongue, and then followed with a glass of water.
- Talk to your doctor if the side effects you are experiencing from donepezil are intolerable. Call your doctor straight away if you are having dizzy spells or fainting, suffering from indigestion or dyspepsia, have a pre-existing lung condition that seems to be getting worse, your stools look like black tar, you are having seizures, or difficulty passing urine.
- Allow four to six weeks before increasing dosage from 5mg to 10mg. People with mild-to-moderate AD should take no more than the maximum recommended dose of 10mg once daily. For people with severe AD, the dose may be increased to 23mg once daily after three months of taking 10mg once daily.
- Do not take any other medications with donepezil until you have checked first that they are compatible.
6. Response and Effectiveness
- Peak concentrations are reached in three hours for the 10mg tablets compared to eight hours for the 23mg tablets.
- Metabolized to a number of active metabolites and accumulates with repeated dosing, reaching maximum concentrations for a particular dosage within 15 days. Metabolism is affected in people who are poor or extensive metabolizers of CYP2D6 substrates.
- Some effects may be noticeable within a few days; however, it may take four to six weeks before any significant differences are apparent. Donepezil may not have the same effects in everybody. Some people seem much better whereas others may only improve slightly or donepezil may just slow the rate of their decline in mental functioning.
Medicines that interact with Donepezil may either decrease its effect, affect how long it works for, increase side effects, or have less of an effect when taken with Donepezil. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.
Common medications that may interact with Donepezil include:
- antipsychotics (such as butyrophenones, phenothiazines, or thioxanthenes) and atypical antipsychotics (eg, olanzapine, quetiapine, ziprasidone)
- beta-blockers, such as atenolol or metoprolol, or other agents that can slow the heartbeat
- corticosteroids, such as prednisone
- medications metabolized by the same enzymes (CYP1A2, CYP2D6, CYP3A4) such as carbamazepine, dexamethasone, phenobarbitone, phenytoin, or rifampin
- medications with anticholinergic properties, such as atropine or benztropine
- neuromuscular blocking agents
Avoid drinking alcohol or taking illegal or recreational drugs while taking Donepezil.
Note that this list is not all-inclusive and includes only common medications that may interact with Donepezil. You should refer to the prescribing information for Donepezil for a complete list of interactions.
Donepezil Revised: 09/2019. Drugs.com https://www.drugs.com/ppa/donepezil.html
Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use donepezil only for the indication prescribed.
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- Drug class: cholinesterase inhibitors
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