A 50-year-old woman with known myasthenia gravis presents with worsening generalized weakness and inability to maintain ventilation. To distinguish a myasthenic crisis from a cholinergic crisis at the bedside, which agent is administered intravenously?

• A Atropine
• B Sugammadex
• C Pralidoxime
• D Edrophonium ✓

Explanation

Edrophonium is a short-acting cholinesterase inhibitor given intravenously as a diagnostic challenge. Improvement in muscle strength within seconds to a few minutes indicates an underdosed state, that is a myasthenic crisis, whereas worsening weakness with fasciculations and muscarinic side effects indicates a cholinergic crisis. Its very brief duration of action makes it safer than neostigmine for this purpose. Atropine treats the muscarinic effects but does not differentiate the two crises.

Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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