Repeat every 10 to 15 minutes to effect with monitoring
Adverse effects and responses
Cholinergic excess
Bradycardia
If symptomatic, atropine IV per ACLS bradycardia dosing
Bronchorrhea
Airway suction and oxygenation support
Seizure
Benzodiazepine treatment
Cardiac toxicity and sodium channel blockade pathway
If QRS widening or ventricular dysrhythmia
Sodium bicarbonate IV bolus
1 to 2 mmol per kg IV
Repeat bolus until QRS narrows or pH target reached
Target pH 7.50 to 7.55 on blood gas
Bicarbonate infusion
150 mmol sodium bicarbonate in 1 L D5W
Rate titration to maintain alkalinization target
Potassium monitoring for hypokalaemia
Decontamination
Activated charcoal
Single dose
1 g per kg orally
Maximum 50 g
Only if airway protected and ingestion within expected benefit window
Pitfalls
Ileus increases aspiration risk
Altered mental status requires airway protection
Urinary retention and ileus
Urinary retention management
Bladder scan confirmation
Catheterization if significant retention
Foley removal plan once delirium resolves
Avoid antimuscarinic agents that worsen retention
Ileus management
Bowel rest if severe distension
Nasogastric tube if vomiting or aspiration risk
Electrolyte correction to support motility
Special Populations
Pregnancy
Pregnancy considerations
Maternal stabilization priority with fetal secondary assessment
Medication safety
Benzodiazepines for severe agitation when needed
Physostigmine use only with toxicology and obstetric consultation
Fetal monitoring
Viable gestation fetal heart rate assessment after maternal stabilization
Geriatric
Older adult considerations
Higher delirium sensitivity from therapeutic dosing
Medication reconciliation for anticholinergic burden
Lower sedation dosing and slower titration
Higher urinary retention risk
Early bladder scan strategy
Post-episode voiding trial planning
Higher arrhythmia risk
Lower threshold for prolonged monitoring
Pediatrics
Pediatric considerations
Weight based dosing for all sedatives and antidotes
Common exposures
Diphenhydramine
Imidazoline and mixed ingestions
Plants and household products
Safeguarding
Non-accidental poisoning consideration in inconsistent history
Social work involvement when indicated
Background
Epidemiology
Epidemiology
Common causes
Antihistamine overdose as frequent exposure source
Polypharmacy anticholinergic burden in older adults
High risk settings
Recreational ingestion of anticholinergic plants
Intentional self-poisoning with sedating antihistamines
Pathophysiology
Mechanism
Muscarinic receptor antagonism
CNS delirium from central M1 blockade
Tachycardia from vagal inhibition
Anhidrosis and hyperthermia from sweat gland blockade
Urinary retention from detrusor relaxation and sphincter tone increase
Mixed mechanisms in common agents
Sodium channel blockade at high dose with diphenhydramine or TCAs
Seizure risk from central toxicity
Therapeutic Considerations
Treatment principles
Supportive care as foundation
Cooling for hyperthermia
Sedation for agitation and seizures
Physostigmine as targeted reversal agent
Best for pure antimuscarinic delirium with normal ECG
Short duration with potential relapse requiring repeat dosing
Avoidance of harms
Physical restraints increasing hyperthermia and rhabdomyolysis risk
Antipsychotics potentially worsening hyperthermia and QT prolongation in some patients
Patient Discharge Instructions
copy discharge instructions
Discharge text
Diagnosis explained as anticholinergic toxicity from medication or plant exposure
Avoid all anticholinergic medications unless prescribed and reviewed
Hydration and rest for 24 to 48 hours
No driving or risky activities for 24 hours after sedation or delirium
Return immediately for confusion, hallucinations, severe agitation, seizure, fainting, chest pain, trouble breathing, inability to urinate, persistent vomiting, or fever
Safe storage of medications and household products out of reach of children
Follow-up plan
Primary care or poison centre follow-up within 24 to 72 hours if symptoms recur
Mental health follow-up if ingestion was intentional
References
Core sources
Evidence sources
StatPearls Anticholinergic Toxicity updated 2023
Tintinalli Emergency Medicine Manual Anticholinergic Toxicity chapter
Narrative review of physostigmine adverse effects 2019
Toxicology practice survey of physostigmine use 2014 and 2015
Decision support and regional protocols
Practice resources
Poison centre physostigmine protocols for dosing and monitoring
Toxicology consultation for mixed overdoses and ECG abnormalities
Institutional procedural sedation and agitation pathways
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.