Donepezil
Drug class: Acetylcholinesterase Inhibitor
Donepezil (ARICEPT)（中文：多奈哌齊）
Common Strengths
Donepezil is available in the following strengths:
- Tablets: 5mg, 10 mg
- Orally Disintegrating Tablets (ODT): 5 mg, 10 mg
Drug Trade Names
- Aricept
Drug Usage
Donepezil is indicated for:
- Treatment of mild, moderate, and severe dementia due to Alzheimer's disease.
- Off-label uses may include vascular dementia and dementia related to Parkinson's disease.
Mechanism of Action
Donepezil works by inhibiting the enzyme acetylcholinesterase. This inhibitor prevents the breakdown of acetylcholine, thereby increasing the concentration of acetylcholine in the brain, which is crucial for memory and cognitive functions.
Route of Administration
Donepezil can be administered orally as tablets or orally disintegrating tablets
Dosages
- Initial: 5 mg once daily at bedtime.
- Maintenance: May increase to 10 mg after 4-6 weeks.
Side Effects
| Frequency | Adverse reactions |
|---|---|
| Common Side Effects | Nausea |
| Diarrhea | |
| Insomnia | |
| Loss of appetite | |
| Serious Side Effects | Bradycardia (slow heart rate) |
| Gastrointestinal Bleeding | |
| Seizures | |
| Severe allergic reactions (e.g. difficulty breathing) |
Pharmacokinetics
Donepezil has a half-life of approximately 70 hours, allowing for once-daily dosing. The onset of action typically occurs within a few weeks, with maximum effects seen after several months of treatment.
Drug Precautions
Pregnancy
There is little information available about the effects of donepezil on pregnancy and fetal development. As a result, healthcare providers typically advise against its use unless necessary.
Breastfeeding
Donepezil is excreted in breast milk; caution should be exercised when administered to nursing mothers.
Children and Elderly
Safety and efficacy have not been established in children. In elderly patients, monitoring for side effects is crucial due to increased sensitivity.
Drug Monitoring Items
Regular monitoring should include:
- Heart rate and rhythm (due to bradycardia risk)
- Gastrointestinal symptoms (to detect potential bleeding)
- Cognitive function assessments to evaluate efficacy
Drug Interactions
Donepezil may interact with various medications, particularly those affecting heart rhythm or gastrointestinal function. Notable interactions include:
- Anticholinergic Medications:
- Anticholinergics (e.g. antihistamines, medications for overactive bladder) may diminish the effects of donepezil, potentially worsening symptoms of Alzheimer's disease due to their opposing mechanisms.
- Cholinergic Agents:
- Combining donepezil with other cholinesterase inhibitor (like neostigmine) can lead to synergistic effects, increasing the risk of cholinergic side effects.
- Beta-Blockers:
- Drugs such as metoprolol and carvedilol may increase the risk of bradycardia when taken with donepezil. Patients should be monitored for heart rate changes.
- Nonsteroidal Anti-Inflammatory Drugs (NSAIDs):
- The concurrent use of NSAIDs (e.g. ibuprofen, naproxen) may increase the risk of gastrointestinal bleeding and ulcers, especially in patients with a history of such conditions.
- CYP450 Enzyme Interactions:
- Donepezil is metabolized by CYP3A4 and to a lesser extent CYP2D6.
- Inhibitors of these enzymes (like ketoconazole and fluoxetine) can increase donepezil levels in the body, while inducers (such as rifampicin and phenytoin) may reduce its effectiveness by increasing its clearance.
FAQ
How Should I Take the Tablet?
Take donepezil once daily at bedtime, with or without food.
What Should I Avoid While Taking?
Avoid other medications that may affect heart rate or gastrointestinal function without consulting a healthcare provider.
What Happens if I Miss a Dose?
If you miss a dose, take it as soon as you remember on the same day; if it is close to the next dose, skip the missed dose and return to your regular schedule.
