What is the best course of action for an elderly patient on Exelon (rivastigmine) experiencing increased hallucinations, excessive drooling, and weakness?

Immediate Management of Rivastigmine Toxicity

Stop Exelon immediately and withhold for 24 hours—this patient is experiencing cholinergic crisis from rivastigmine overdose, characterized by the classic triad of excessive drooling (salivation), weakness, and hallucinations. 1

Recognition of Cholinergic Crisis

The FDA label explicitly identifies this presentation as rivastigmine overdose symptoms:

• Excessive salivation (drooling) is a hallmark cholinergic symptom 1
• Weakness represents the muscular effects of cholinesterase excess 1
• Hallucinations are specifically listed as an overdose symptom 1
• This constellation indicates cholinergic crisis requiring immediate drug cessation 1

Immediate Actions (First 24 Hours)

Hold all rivastigmine doses for 24 hours as recommended by the FDA for symptomatic overdose, given the drug's 1-hour half-life and 8-10 hour duration of acetylcholinesterase inhibition 1

Supportive Care

• Monitor for respiratory depression and bradycardia, as severe cholinergic crisis can progress to respiratory muscle involvement and cardiovascular collapse 1
• Administer antiemetics if severe nausea/vomiting develops, as these are common overdose symptoms 1
• Avoid anticholinergic agents (like glycopyrrolate) unless absolutely necessary, as atypical blood pressure and heart rate responses can occur 1

Root Cause Analysis

This likely represents one of two scenarios:

Scenario 1: Dose Accumulation

• Low body weight or renal/hepatic impairment can cause rivastigmine accumulation, as blood levels vary significantly with these factors 1
• Elderly patients with moderate-to-severe renal impairment may only tolerate lower doses 1

Scenario 2: Recent Dose Increase

• Rapid titration or recent dose escalation without adequate monitoring can precipitate cholinergic symptoms 2
• The patient may have been switched from a lower to higher dose patch without proper titration 2

Restarting Strategy After 24-Hour Hold

Resume at 50% of the previous dose after symptoms completely resolve (typically 24-48 hours) 1

Specific Restart Protocol

• If patient was on 6 mg oral twice daily: restart at 3 mg twice daily 1
• If patient was on 9.5 mg/24h patch: restart at 4.6 mg/24h patch 2
• Titrate slowly over 4+ weeks before considering any dose increase 2
• Take with food to minimize gastrointestinal side effects 2

Managing the Hallucinations Post-Crisis

Once cholinergic symptoms resolve and rivastigmine is restarted at lower dose:

If Hallucinations Persist After Toxicity Resolves

Initiate quetiapine 12.5-25 mg twice daily as the preferred antipsychotic for elderly dementia patients with hallucinations 3, 4

Rationale for quetiapine over alternatives:

• Lower risk of extrapyramidal symptoms compared to haloperidol or risperidone 3, 4
• More sedating, which helps with agitation 3, 4
• Safer in patients who may have underlying Lewy body features 4

Alternative if Quetiapine Not Tolerated

Olanzapine 2.5 mg at bedtime can be used, though it carries higher metabolic risks 3, 4

Critical Monitoring Parameters

During the 24-Hour Hold

• Vital signs every 4 hours: heart rate, blood pressure, respiratory rate 1
• Salivation and weakness: should improve within 8-10 hours as acetylcholinesterase inhibition wears off 1
• Mental status: hallucinations may persist longer but should not worsen 1

After Restarting Rivastigmine

• Daily assessment for first week: monitor for return of cholinergic symptoms (nausea, vomiting, diarrhea, salivation) 2, 1
• Weekly assessment for 4 weeks: ensure tolerance before any dose adjustment 2
• Assess renal and hepatic function if not recently checked, as impairment necessitates lower maintenance doses 1

Common Pitfalls to Avoid

Do not add antipsychotics during active cholinergic crisis, as hallucinations from rivastigmine toxicity will resolve with drug cessation—adding antipsychotics risks polypharmacy complications 1

Do not restart at the same dose that caused toxicity—this will simply recreate the problem 1

Do not use haloperidol as first-line for hallucinations in this population due to high extrapyramidal symptom risk and potential for Lewy body sensitivity 3, 4

Avoid benzodiazepines for hallucination management, as they can worsen delirium and cause paradoxical agitation in elderly patients 4

Long-Term Management Considerations

Once stabilized on lower rivastigmine dose:

• Maintain at lowest effective dose that controls cognitive symptoms without cholinergic side effects 1
• Consider body weight: patients with low body weight require more careful titration and monitoring 1
• Reassess need for dose increase only after 6-12 months of stability at current dose 2