Cholinesterase inhibitors — donepezil, rivastigmine, galantamine — are the symptomatic treatment for Alzheimer's disease. They work by addressing one specific aspect of the pathology: the basal forebrain cholinergic deficit that emerges as the disease progresses.
- Class
- Acetylcholinesterase Inhibitors (AChEIs)
- Mechanism
- Inhibit acetylcholinesterase → reduce ACh breakdown → enhance cholinergic signaling. Targets cholinergic deficit central to Alzheimer's pathology.
- Typical dose
- Drug-specific
- Half-life
- Drug-specific
- FDA indications
- Mild to moderate Alzheimer's disease (donepezil also moderate-severe), Parkinson's disease dementia (rivastigmine), dementia with Lewy bodies (off-label)
- Key adverse effects
- GI (nausea, vomiting, diarrhea, anorexia, weight loss — dose-dependent), bradycardia, syncope, vivid dreams/nightmares, insomnia (if AM dosed), urinary incontinence, muscle cramps
- Representative agents
- Donepezil (Aricept), rivastigmine (Exelon — oral or patch), galantamine (Razadyne — also nicotinic allosteric modulator)
Modest symptomatic benefit — slow cognitive decline by 6-12 months on average, do not modify underlying disease. GI side effects are dose-limiting. Patches (rivastigmine) reduce GI burden. Continue as long as benefit perceived; consider discontinuation in advanced disease.
The nucleus basalis of Meynert and adjacent cholinergic neurons project widely to cortex. In Alzheimer's, these neurons progressively die, reducing cortical acetylcholine signaling. AChEIs block acetylcholinesterase, the enzyme that degrades synaptic ACh. The result is preserved ACh in the synapse, partial compensation for the dying neurons, and modest cognitive benefit.
Cholinesterase inhibitors treat the cholinergic deficit of Alzheimer's disease — they do not modify the underlying pathology, but they support remaining cholinergic signaling.
Mechanism note: Cholinesterase inhibitors offer modest symptomatic support by propping up a failing cholinergic system — real but limited benefit, GI-limited tolerability, and no effect on disease progression.
The benefit is real but modest. AChEIs do not modify the underlying disease; they do not prevent neuronal death; they do not reverse pathology. They slow the decline. Cognitive testing scores typically improve modestly, decline is delayed by approximately 6-12 months on average, and ADL preservation improves. For the patient and family, this can be meaningful — but the eventual trajectory of the disease is not changed.
Expectations management is one of the most important parts of prescribing AChEIs. Families often hope for "a cure" or for substantial cognitive recovery. The honest framing: these medications slow the disease modestly, may improve attention and engagement, and are worth trying — but the underlying disease will progress.
GI side effects are dose-limiting for many patients. Nausea, vomiting, diarrhea, anorexia, weight loss — particularly prominent during titration. Strategies: slow titration, take with food, use the transdermal patch (rivastigmine) to bypass GI absorption. Weight loss can be substantial; monitor and intervene with nutrition support if needed.
Other adverse effects: bradycardia and syncope (vagal effects), vivid dreams or nightmares (especially when dosed at bedtime), urinary incontinence, muscle cramps. The drugs are cholinergic — caution in patients with COPD, asthma, peptic ulcer disease, or significant bradyarrhythmias.
Continue AChEIs as long as benefit is perceived. In advanced disease, when meaningful function is lost, consider discontinuation — though this is its own difficult conversation.