Typical Doses of Medications for Alzheimer's Disease Treatment
The standard medications for Alzheimer's disease include cholinesterase inhibitors (donepezil, rivastigmine, galantamine) and memantine, with specific dosing regimens that should be followed for optimal efficacy and tolerability. 1
Cholinesterase Inhibitors
Donepezil (Aricept)
- Starting dose: 5 mg once daily 1, 2
- Increase to 10 mg once daily after 4-6 weeks if well tolerated 1, 2
- For moderate to severe Alzheimer's disease, doses up to 23 mg once daily may be considered 2
- Take with or without food; taking with food can reduce gastrointestinal side effects 1
- Most common side effects: nausea, vomiting, diarrhea, and initial agitation that typically subsides 1
Rivastigmine (Exelon)
- Starting dose: 1.5 mg twice daily (3 mg/day) 1
- Increase by 1.5 mg twice daily (3 mg/day) every 4 weeks as tolerated 1
- Maximum dose: 6 mg twice daily (12 mg/day) 1
- Higher doses are more efficacious but have more side effects 1
- Take with food to minimize gastrointestinal side effects 1
- Most common side effects: nausea, vomiting, diarrhea, weight loss, headaches, dizziness 1
Galantamine (Reminyl)
- Starting dose: 4 mg twice daily (8 mg/day) with morning and evening meals 1
- Increase to 8 mg twice daily (16 mg/day) after 4 weeks 1
- Consider increase to 12 mg twice daily (24 mg/day) based on individual assessment of benefit and tolerability 1
- Contraindicated in patients with hepatic or renal impairment 1
- Take with food to minimize gastrointestinal side effects 1
Tacrine (Cognex)
- Now considered a second-line agent due to hepatotoxicity 1
- Starting dose: 10 mg four times daily (40 mg/day) 1
- Increase by 10 mg four times daily every 4 weeks 1
- Maximum dose: 40 mg four times daily (160 mg/day) 1
- Requires biweekly liver function tests during dose escalation and every 3 months thereafter 1
- Not recommended as first-line therapy due to high side effect profile and monitoring requirements 1
Other Medications
Memantine
- Dosage: 20 mg/day for moderate to severe Alzheimer's disease 1
- Shows statistically significant improvement in cognition for moderate to severe Alzheimer's disease 1
- Can be used alone or in combination with cholinesterase inhibitors 1
- Side effects include dizziness, headache, confusion, and constipation 1
Vitamin E
- Dosage: 2,000 IU daily 1
- May slow progression of functional symptoms 1
- Current expert consensus recommends its use as an adjunct therapy 1
Practical Dosing Considerations
- Assessment period: Observation for 6-12 months is usually necessary to assess potential benefit of cholinesterase inhibitors 1
- Discontinuation criteria: Consider stopping if side effects persist, adherence is poor, or deterioration continues at pre-treatment rate after 6-12 months 1
- Switching medications: Patients who do not respond to one cholinesterase inhibitor may respond to another 1
- Dose optimization: Higher doses generally provide greater efficacy but with increased side effects; balance must be achieved 3
- For donepezil specifically, the 10 mg dose has shown greater efficacy than 5 mg, particularly for activities of daily living 4
Common Pitfalls and Caveats
- Unrealistic expectations: Before initiating treatment, communicate the expected modest benefits to patients and families 1
- Inadequate monitoring: Brief mental status tests are relatively insensitive measures of cholinesterase inhibitor effects; use comprehensive assessments 1
- Premature discontinuation: Benefits may not be apparent immediately; allow adequate trial period 1
- Failure to manage side effects: Most gastrointestinal side effects can be minimized by taking medications with food and gradual dose titration 1
- Overlooking drug interactions: Cholinesterase inhibitors may interact with anticholinergic medications and succinylcholine-type muscle relaxants 2
Careful dose titration, monitoring for side effects, and regular assessment of response are essential components of optimal pharmacotherapy for Alzheimer's disease 1.