Donepezil Dosing for an 89-Year-Old Patient with Sundowning
Start donepezil at 5 mg once daily in the evening, just before bedtime, and titrate to 10 mg after 4-6 weeks if tolerated; no dose adjustment is needed for renal impairment. 1
Initial Dosing
Begin with 5 mg once daily in the evening, taken just prior to retiring. This can be administered with or without food 1. This starting dose applies regardless of whether the patient has mild, moderate, or severe Alzheimer's disease 1.
For this 89-year-old patient with sundowning specifically, evening dosing is particularly appropriate. Evidence from a case report demonstrated marked reduction in evening agitation and improved activity patterns when donepezil was given for sundowning in dementia with Lewy bodies 2. The evening timing aligns with both FDA recommendations and the clinical goal of addressing nocturnal behavioral symptoms.
Titration Schedule
After 4-6 weeks at 5 mg daily, increase to 10 mg once daily if the patient tolerates the initial dose 1. This is the maximum recommended dose for mild to moderate Alzheimer's disease and represents the standard therapeutic target 1.
The 23 mg dose is reserved for moderate to severe disease and requires patients to be stable on 10 mg for at least 3 months before escalation 1. However, for an 89-year-old patient, the 10 mg dose is typically sufficient, as the 23 mg formulation carries significantly higher rates of cholinergic side effects (nausea: 11.8% vs 3% at 10 mg) 1.
If escalation to higher doses becomes necessary, consider intermediate titration strategies. Research shows that using 15 mg for 4 weeks or alternating 10 mg/23 mg on alternate days before full escalation to 23 mg significantly reduces cholinergic adverse events, particularly nausea 3.
Renal Function Considerations
No dose adjustment is required for renal impairment, including patients on dialysis 4, 5. Donepezil has been studied in patients with moderately to severely impaired renal function and demonstrated safety and tolerability without dose modification 4.
A case series of 5 chronic hemodialysis patients with moderate Alzheimer's disease successfully used donepezil starting at 2.5 mg daily, then increased to 5 mg daily after 1 month, with good tolerability and no toxicity over 10 years of follow-up 6. While this suggests even more conservative dosing is possible in dialysis patients, the standard 5 mg starting dose remains appropriate for most elderly patients with renal impairment 4.
Safety Monitoring
The most common adverse events are gastrointestinal (diarrhea, nausea, vomiting) and are dose-related 1, 4. These effects occur more frequently with 10 mg than 5 mg 7, 8. The incidence of GI adverse events with donepezil is comparable to placebo when started at 5 mg 4.
Monitor for cardiovascular effects, particularly bradycardia or heart block, as cholinesterase inhibitors have vagotonic effects on cardiac conduction 1. Syncope has been reported with donepezil use 1.
If insomnia or sleep disturbances emerge (despite evening dosing being standard), consider switching to morning administration or extending the time period before dose escalation from 5 mg to 10 mg 4.
Evidence Quality
The FDA labeling provides the strongest directive for dosing 1. This is supported by high-quality evidence from 24 studies showing donepezil improves cognition (ADAS-cog) and global function (CIBIC-plus) in Alzheimer's disease, though the average ADAS-cog improvement did not reach the clinically significant threshold of 4 points 7, 8. The CIBIC-plus improvements were clinically meaningful 7. The 2025 Korean Dementia Association guidelines strongly recommend cholinesterase inhibitors for AD based on moderate evidence 9.
Common Pitfalls
- Do not split, crush, or chew the 23 mg tablet if prescribed (though this is unlikely needed for your patient) 1
- Do not skip the 4-6 week stabilization period at 5 mg before advancing to 10 mg 1
- Do not assume renal impairment requires dose reduction—it does not 4, 5
- Do not discontinue therapy if the patient continues to deteriorate—donepezil is for symptomatic treatment and does not stop disease progression 5