A toxic alkaloid extracted from belladonna and other members of thenightshade family, it is typically used to dilate the eye and to stopmuscular spasms.

Pharmacologic action: Parasympatholytic. Competitive blockade of acetylcholine at muscarinic receptors. Increases sinus node automaticity and AV conduction.

Uses: Treat bradycardia, asystole, and AV block

Dose: 0.5 - 1.0 mg for bradycardia every 3 - 5 min to a total dose of 0.04 mg/kg. Doses smaller than 0.5 mg can cause a paradoxical bradycardia due to sympathomimetic effects Typically 3 mg is adequate to completely block vagal effects Atropine is well absorbed via endotracheal route - administer 1-2 mg diluted in 10 mL sterile water or normal saline.

Potential complications: 1. Tachyarrhythmias 2. Exacerbation of myocardial ischaemia 3. Low dose may cause paradoxical bradycardia 4. Dry mouth, urinary retention, flushed and hot skin 5. Crosses blood-brain barrier which can cause delirium

Note: The denervated heart will not respond to atropine.

(15 Mar 2000)