Benztropine

Benztropine is used in acute dystonic reactions, it blocks striatal cholinergic receptors, thus helping to balance the cholinergic and dopaminergic activity. Drugs responsible for dystonic reactions other than antipsychotics include:

• Antiemetics —  e.g. metaclopramide, proclorperazine
• Antidepressants and serotonin receptor agonists — e.g. SSRIs, buspirone, sumitriptan
• Antibiotics — e.g. erythromycin
• Antimalarials — e.g. chloroquine
• Anticonvulsants — e.g. carbamazepine, vigabatrin
• H2 receptor antagonists — e.g. ranitadine, cimetidine
• Recreational drugs — e.g. cocaine

Management:

• ABCDE – patient may have laryngospasm.
• Benztropine:
  • First line treatment of acute dystonic reactions
  • Response is often dramatic and generally occurs in 5-20mins
  • if symptoms persist after 15-30mins a second dose can be given.
  • if symptoms persist and are not improving after second dose consider the possibility of an alternative diagnosis.
  • Adult: 1-2mg by slow IV injection – if IV is not possible it can be given IM but may take 30 minutes to work.
  • Child: 0.02mg/kg to maximum of 1mg

References

• Campbell, D. (2001). The management of acute dystonic reactions. Australian Prescriber. 24(1), 19-20.
• Fines, R. Brady, W. & DeBehnke. (1997). Cocaine-Associated Dystonic Reaction. American Journal of Emergency Medicine. 15(5),  513-516. PMID: 9270394
• Khan, N. & Razzak, J. (2006). Abdominal pain with rigidity secondary to the anti-emetic drug metaclopramide. The Journal of Emergency Medicine. 30(4), 411-413. PMID: 16740451
• Nochimson, G. (2009). Toxicity, Medication-Induced Dystonic Reactions. http://emedicine.medscape.com/article/814632-overview
• Yis, U. et.al. (2005). Metaclopramide induced dystonia in children: two case reports. European Journal of Emergency Medicine. 12, 117-119. PMID: 15891443