Keywords: anticholinergic, physostigmine (PubMed Search)
Posted: 11/18/2010 by Fermin Barrueto, MD
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In the setting of a patient suffering from an anticholinergic overdose with hallucinations/agitation, it may be beneficial to administer the antidote: Physostigmine. Many hesitate simply because they have never administered before or there may be doubt in the diagnosis. Here is the skinny:
1) Anticholinergic OD seen in following meds: diphenhydramine (Benadryl), dimenhydrinate (Dramamine), scopolamine, benztropine (Cogentin), some plants like datura stromonium (thorn apple)
2) Physostigmine 1mg IV slowly over a REAL 5 min. Administer to fast and patient may seize. Maximum dose of 2mg IV.
3) Contraindications: suspicion of TCA OD (anectdotal and from old case report) - screening EKG should be done prior to administration of physostigmine. Also glaucoma, closed angle, obstructive uropathy.
Remember your clinical endpoint needs to be measurable, thus hallucinations and agitation should be reversed. No indication if the patient is only experiencing dry mouth or other more mild anticholinergic symptoms.
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