A patient with myasthenia gravis who is also asthmatic requires an anticholinesterase. Neostigmine is preferred over physostigmine in this context because:
- A Neostigmine is a quaternary ammonium compound that does not cross the BBB and additionally stimulates nicotinic receptors at the NMJ ✓
- B Neostigmine crosses the blood-brain barrier and improves central motor control
- C Neostigmine selectively inhibits butyrylcholinesterase without affecting acetylcholinesterase
- D Neostigmine has a longer duration of action than physostigmine by irreversibly inhibiting AChE
Correct answer: A. Neostigmine is a quaternary ammonium compound that does not cross the BBB and additionally stimulates nicotinic receptors at the NMJ
Explanation
Neostigmine is a quaternary nitrogen compound; its charged nature prevents it from crossing the blood-brain barrier, avoiding central side effects. In addition to inhibiting AChE, neostigmine directly stimulates nicotinic receptors at the neuromuscular junction — a direct agonist effect that enhances its therapeutic efficacy in myasthenia gravis. Physostigmine is a tertiary amine that crosses the BBB and is used for CNS anticholinergic toxicity. Both drugs reversibly inhibit AChE.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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