Methacholine has methyl group in its structure. It is more resistant to hydrolysis by choline esterase. It has both muscarinic and nicotinic actions (very mild nicotinic actions )
Muscarinic actions are prominent on CVS (M2).
Duration of action is 15-20 minutes. Longer duration of action as compared to acetylcholine
1. Given subcutaneously for the relief of paroxysmal atrial tachycardia
Previously, it was said to be effective in paroxysmal atrial tachycardia, now better drugs are available like adenosine, Calcium channel blockers, esmolol, etc.
2. Diagnosis of belladonna poisoning
3. Diagnosis of bronchial hyperactivity