1. Introduction
Donepezil is a cholinesterase inhibitor used to manage the symptoms of Alzheimer’s disease and other dementias. It works by inhibiting acetylcholinesterase, the enzyme that breaks down acetylcholine, thereby increasing acetylcholine levels in the brain. This improves communication between nerve cells, helping to alleviate cognitive symptoms such as memory loss and confusion.
2. Indications
- Approved Indications:
- Mild, moderate, and severe Alzheimer’s disease.
- Dementia associated with Parkinson’s disease (off-label in certain cases).
- Off-Label Uses:
- Lewy body dementia.
- Vascular dementia (limited evidence of benefit).
3. Dosage
- Adults:
- Initial dose: 5 mg orally once daily.
- Maintenance dose: After 4–6 weeks, may increase to 10 mg once daily if tolerated.
- Maximum dose: 23 mg once daily (extended-release formulation).
- Elderly:
- Same as adult dosing; monitor for increased sensitivity to side effects.
4. Administration
- Take orally once daily, preferably at bedtime to minimise side effects such as nausea.
- Can be taken with or without food.
- Extended-release tablets must be swallowed whole; do not crush or chew.
5. Forms Available
- Tablets: 5 mg, 10 mg.
- Orally disintegrating tablets (ODT): 5 mg, 10 mg.
- Extended-release tablets: 23 mg.
6. Side Effects
6.1. Common Side Effects
- Nausea and vomiting.
- Diarrhoea.
- Insomnia.
- Muscle cramps.
- Fatigue.
6.2. Less Common Side Effects
- Dizziness.
- Loss of appetite.
- Headache.
6.3. Rare but Serious Side Effects
- Bradycardia (slow heart rate).
- Syncope (fainting).
- Gastrointestinal bleeding (particularly in patients with a history of ulcers or those taking NSAIDs).
- Seizures.
7. Warnings
- Cardiac Effects: May cause bradycardia or heart block, especially in patients with pre-existing cardiac conditions.
- Gastrointestinal Effects: Increased risk of ulcers and bleeding, particularly in patients with a history of gastrointestinal disease or those taking NSAIDs.
- Seizure Risk: Use cautiously in patients with a history of seizures.
8. Precautions
- Monitor for signs of fainting or dizziness due to its potential to slow heart rate.
- Use with caution in patients with asthma or COPD, as it may increase bronchoconstriction.
- Avoid abrupt discontinuation, as this may worsen symptoms temporarily.
9. Interactions
- Drug-Drug Interactions:
- Anticholinergic drugs (e.g., atropine, oxybutynin): Reduced efficacy of donepezil.
- NSAIDs: Increased risk of gastrointestinal bleeding.
- Beta-blockers: Increased risk of bradycardia.
- CYP3A4 inhibitors (e.g., ketoconazole, erythromycin): May increase donepezil levels.
- CYP3A4 inducers (e.g., rifampin, carbamazepine): May reduce donepezil levels.
10. Monitoring Parameters
- Improvement in cognitive symptoms (e.g., memory, orientation, and language).
- Monitor for side effects, especially gastrointestinal symptoms, dizziness, and bradycardia.
- Periodic evaluation of liver function tests.
11. Use in Children
- Not approved for use in children due to lack of evidence for safety and efficacy.
12. Use in Pregnancy
- Category C: Use only if the potential benefit outweighs the risk. No adequate studies in pregnant women.
13. Use in Elderly
- Widely used in elderly patients; start at the lowest dose and titrate slowly due to increased sensitivity to side effects.
14. Use in Kidney Disease
- No specific dose adjustment required, as donepezil is minimally excreted renally.
15. Use in Liver Disease
- Use with caution in patients with hepatic impairment, as metabolism may be affected. No specific dosage adjustment is required in mild to moderate liver disease.
16. Patient Counselling Points
- Take donepezil at the same time each day, preferably at bedtime.
- Report symptoms such as severe nausea, vomiting, or fainting immediately.
- Inform your doctor of any other medications, especially anticholinergics or beta-blockers.
- Do not stop the medication abruptly without consulting your healthcare provider.
- While donepezil helps manage symptoms, it does not cure Alzheimer’s disease.
17. Table of Brand Names, Manufacturers, and Prices
Brand Name | Manufacturer | Price (USD) |
---|---|---|
Aricept | Eisai/Pfizer | $60–100 (30 tablets, 10 mg) |
Generic Donepezil | Various | $15–40 (30 tablets, 10 mg) |
Aricept ODT | Eisai | $70–110 (30 tablets, 10 mg) |
18. FAQs (15 Questions)
- What is donepezil used for?
Donepezil is used to manage the symptoms of Alzheimer’s disease, such as memory loss and confusion. - How does donepezil work?
It increases acetylcholine levels in the brain by inhibiting acetylcholinesterase, improving communication between nerve cells. - Can donepezil cure Alzheimer’s disease?
No, it helps manage symptoms but does not stop or reverse the progression of the disease. - What are the common side effects of donepezil?
Nausea, diarrhoea, insomnia, and muscle cramps are common side effects. - How should donepezil be taken?
Take it once daily, preferably at bedtime, with or without food. - What should I do if I miss a dose of donepezil?
Skip the missed dose and take the next dose at the usual time. Do not double the dose. - Can donepezil cause heart problems?
Yes, it may cause bradycardia or heart block in some patients, especially those with pre-existing conditions. - Is donepezil safe for elderly patients?
Yes, it is widely used in elderly patients but requires careful monitoring for side effects. - Does donepezil interact with other medications?
Yes, it interacts with anticholinergic drugs, NSAIDs, beta-blockers, and certain CYP3A4 inhibitors/inducers. - Can donepezil be stopped suddenly?
Sudden discontinuation may temporarily worsen symptoms. Consult a doctor before stopping. - How long does it take for donepezil to work?
Improvements in symptoms may be noticeable within a few weeks, but full effects may take up to 12 weeks. - Can donepezil cause gastrointestinal bleeding?
Yes, especially in patients taking NSAIDs or with a history of ulcers. - Is donepezil safe during pregnancy?
Use only if the benefits outweigh the risks, as its safety in pregnancy has not been well established. - Can donepezil cause drowsiness?
It typically does not cause drowsiness but may cause dizziness in some patients. - How should donepezil be stored?
Store at room temperature, away from moisture and heat.