A myasthenia gravis patient on pyridostigmine presents with worsening weakness. To distinguish myasthenic crisis from cholinergic crisis at the bedside, which drug is traditionally used?
- A Atropine
- B Pralidoxime
- C Edrophonium ✓
- D Sugammadex
Correct answer: C. Edrophonium
Explanation
Edrophonium is a very short acting acetylcholinesterase inhibitor. In myasthenic crisis it transiently improves muscle strength within seconds to minutes, whereas in cholinergic crisis it worsens weakness and triggers muscarinic features like fasciculations, sweating and bradycardia. Atropine treats muscarinic symptoms but does not differentiate the two states, and pralidoxime is reserved for organophosphate poisoning. The short duration of action makes edrophonium safe for this diagnostic use.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
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