Benztropine Overdose: Symptoms and Management
Benztropine overdose produces classic anticholinergic toxicity requiring immediate supportive care, with physostigmine reserved for severe cases with life-threatening CNS or peripheral manifestations. 1, 2
Clinical Presentation of Anticholinergic Toxicity
The hallmark features of benztropine overdose mirror atropine poisoning and include: 2
Central Nervous System Effects
- CNS depression preceded or followed by stimulation 2
- Confusion, nervousness, listlessness 2
- Hallucinations (especially visual) 2, 3
- Delirium and toxic psychosis (particularly in patients already on neuroleptic drugs) 2, 3
- Agitation and combative behavior 4
- Seizures and convulsions 2
- Progression to coma in severe cases 2
Peripheral Anticholinergic Signs
- Hot, dry, flushed skin (distinguishing feature from sympathomimetic toxicity which causes diaphoresis) 1, 2
- Mydriasis (dilated pupils) and blurred vision 1, 2
- Dry mouth 2
- Decreased or absent bowel sounds 1
- Anhidrosis (absence of sweating) 2
- Urinary retention (dysuria) 2
Cardiovascular Effects
Other Manifestations
- Hyperthermia (can be severe) 1, 2
- Tachypnea 1
- Muscle weakness and ataxia 2
- Numbness of fingers 2
- Respiratory arrest in severe cases 2
Critical pitfall: The psychosis can persist for prolonged periods—case reports document anticholinergic delirium lasting up to 9 days due to intermittent drug absorption from the GI tract. 5, 6
Treatment Algorithm
Immediate Stabilization
Discontinue the precipitating agent and ensure airway, breathing, and circulation are secured. 1
First-Line Management: Supportive Care
Gastrointestinal decontamination (if patient is alert and not convulsing): 2
- Induce emesis or perform gastric lavage
- Contraindicated in precomatose, convulsive, or psychotic states 2
Benzodiazepines for agitation and seizures: 1, 4
- Primary sedative agent of choice
- Avoid phenothiazines due to their anticholinergic properties 3
Supportive measures: 2
Short-acting barbiturates may be used cautiously for CNS excitement, but avoid subsequent depression 2
Second-Line: Physostigmine (Antidote)
Physostigmine salicylate 1-2 mg SC or IV is indicated ONLY for severe anticholinergic toxicity with significant CNS effects or life-threatening peripheral manifestations. 1, 2
- Pediatric dose: 0.02 mg/kg IV 1
- A second injection may be given after 2 hours if required 2
- Physostigmine reverses both central and peripheral anticholinergic symptoms 2, 3
Absolute contraindications to physostigmine: 1
- Cardiovascular disease
- Asthma
- Gangrene
- Diabetes
- Mechanical obstruction of intestine or urinary tract
Management of Specific Complications
Hyperthermia: External cooling measures 1
Mydriasis and cycloplegia: Local miotic agents 2
QRS prolongation or dysrhythmias: Sodium bicarbonate 1
Avoid succinylcholine in patients with anticholinergic crisis as it may cause prolonged paralysis 1
Common Pitfalls to Avoid
- Do not use phenothiazines for sedation as they have anticholinergic properties that worsen toxicity 3
- Do not routinely administer physostigmine to all anticholinergic overdoses—reserve for severe, life-threatening cases only 1, 2
- Do not assume brief duration of symptoms—anticholinergic toxicity from benztropine can persist for days due to prolonged GI absorption 5, 6
- Do not overlook the possibility of co-ingestions that may complicate the clinical picture 2
Fatalities from benztropine overdose are rare with appropriate supportive care, though the drug can cause major morbidity requiring intensive care and prolonged hospitalization. 4, 7