Neostigmine used for reversal of non-depolarizing block must always be accompanied by glycopyrrolate or atropine. Which specific adverse effect of neostigmine necessitates this?

• A Neostigmine causes CNS excitation that is prevented by anticholinergics
• B Neostigmine displaces calcium from sarcoplasmic reticulum, causing muscle rigidity
• C Neostigmine prolongs the QT interval, and anticholinergics prevent this
• D Neostigmine increases ACh at all cholinergic synapses including muscarinic ones, causing bradycardia, bronchospasm, and hypersalivation ✓

Explanation

Neostigmine inhibits acetylcholinesterase throughout the body, increasing ACh at both nicotinic NMJs (desired reversal) and muscarinic receptors (undesired). Muscarinic activation causes bradycardia, increased airway secretions, bronchospasm, increased GI motility, miosis, and bladder contraction. Glycopyrrolate (preferred because its quaternary structure prevents CNS entry) or atropine is co-administered to block these muscarinic side effects. Glycopyrrolate is paired with neostigmine because their onset profiles are matched.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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