- OVERDOSE: Data are limited. Based on its cholinergic effects, typical findings might include muscarinic actions consisting of: miosis, flushing, bradycardia, bronchospasm, increased bronchial secretions, involuntary urination and/or defecation, sweating, lacrimation, hypotension, and/or seizures. Because of its high degree of selectivity for AChE in the CNS and less peripheral selectivity, overdoses would be expected to exhibit more CNS-related symptomatology, including extrapyramidal effects. ADVERSE EFFECTS: Diarrhea, loss of appetite, nausea, vomiting, muscle cramps, insomnia, and fatigue
Range of Toxicity:
- TOXICITY: Overdoses of 45 mg and 50 mg resulted in nausea, vomiting, and diarrhea in two elderly adults, one of these patients developed persistent bradycardia (HR in the 40’s); both had uneventful recoveries. THERAPEUTIC: ADULT dose is 5 to 10 mg orally once daily. CHILDREN: Safety and effectiveness not established.
- Support: Treatment is symptomatic and supportive.
- Decontamination: Consider activated charcoal if the patient is able to maintain airway or if airway is protected.
- Atropine: Atropine sulfate is the drug of choice to treat muscarinic effects such as bradycardia, bronchorrhea, and bronchospasm. ADULTS – 1 to 2 mg IV repeated every 3 to 60 min as needed. CHILD – 0.05 milligram/kilogram up to 4 milligrams (usual dose 1 milligram) ,IM/IV every 10 to 30 minutes.
- Bronchospasm: Albuterol, epinephrine
- Seizure: IV benzodiazepines, barbiturates
- Hypotensive episode: IV 0.9% NaCl 10 to 20 ml/kg, dopamine, norepinephrine, dobutamine. Consider central venous pressure or pulmonary artery monitoring.
- Bradycardia: Atropine
- Hemodialysis: Because of donepezil’s large volume of distribution and high degree of protein binding (94% to 96%), hemodialysis is not expected to be of benefit.
- Monitoring of patient: Monitor vital signs, ECG, fluid and electrolyte balance, especially with vomiting and diarrhea. Monitor and support respiratory and cardiovascular function.