Normally used to ameliorate dyskinesia from antipsychotics but has been used for recreational purposes. Benztropine is a potent anticholingeric in overdose. You may also use it yourself as an antidote for an acute dystonic reaction.
It contains a combination of atropine (active part of atropine) and an antihistamine (diphenylmethyl) therefore it acts as an anticholinergic as well as a antihistaminergic with dopamine reuptake inhibition.
- Rapidly absorbed
- Onset of action is within 1 – 2 hours
- Possible hepatic metabolism but excreted in the urine
- Rarely required
- Any overdose can cause an anticholinergic toxidrome that will likely require supportive care.
- Effects are usually seen within 6 hours and may last anywhere between 12 hours to 5 days.
- Sometimes therapeutic doses can cause an anticholinergic toxidrome.
- Controlling the delirium can be difficult, things to consider include
- Titrated doses of benzodiazepines e.g. diazepam 2.5 – 5 mg every 5 minutes IV until gentle sedation is achieved
- Physical restraint
- Bladder scan and a catheter for urinary retention
- Cautious use of physostigmine
- Screening: 12 lead ECG, BSL, Paracetamol level
- EUC, CT brain and lumbar puncture maybe required in the undifferentiated patient
- 50g of activated charcoal maybe given to the alert and cooperative patient who has ingested benztropine in the previous 2 hours.
- Once delirium has occurred it will be very difficult to administer and should be avoided.
- Not clinical useful
- Physostigmine can be used both diagnostically (if patient returns to normal post administration) or an adjunct if anticholinergic delirium is not controlled with benzodiazepines. Caution is advised as it can precipitate a cholinergic crisis if given inappropriately.
- Patients who are symptomatic will need 1:1 nursing in an HDU or equivalent environment until symptoms have resolved.
References and Additional Resources:
- Tox conundrum: Acute Dystonic Reaction
- Tox conundrum: A fumbling, Mumbling Mess
- Tox Flashcard – Anticholinergic Toxidrome
- Anticholinergic song
DRUGS and TOXICANTS
Dr Neil Long BMBS FACEM FRCEM FRCPC. Emergency Physician at Kelowna hospital, British Columbia. Loves the misery of alpine climbing and working in austere environments (namely tertiary trauma centres). Supporter of FOAMed, lifelong education and trying to find that elusive peak performance.