Neostigmine vs Sugammadex

Current · V5 (2025) → I3.i 1 exam appearance

2026A Q15

Exam question

Compare and contrast neostigmine and sugammadex using the following headings:
a) drug class and mechanism of action (30% of marks),
b) indications for use (15% of marks),
c) dose and dosing considerations (15% of marks),
d) pharmacodynamics and adverse effects (40% of marks).

CICMWrecks answer

Master answer

Compare Neostigmine & Sugammadex in the Pharmacopeia

a) Drug class and mechanism of action (30%)

Feature	Neostigmine	Sugammadex
Class	Reversible acetylcholinesterase inhibitor (carbamate anticholinesterase).	Modified γ-cyclodextrin; selective relaxant-binding agent.
Primary mechanism	Carbamylates acetylcholinesterase → slows acetylcholine breakdown → ↑ acetylcholine concentration at the neuromuscular junction.	Encapsulates free aminosteroid neuromuscular blocker, especially rocuronium and vecuronium, in plasma.
How reversal occurs	More acetylcholine competes with residual non-depolarising blocker at nicotinic receptors.	Rapid fall in free plasma relaxant creates a concentration gradient away from the neuromuscular junction → blocker dissociates from nicotinic receptors and diffuses into plasma.
Important limitation	Does not remove the blocker; requires some spontaneous recovery and has a ceiling effect once acetylcholinesterase is maximally inhibited.	Only reverses drugs it can bind effectively; clinically used for rocuronium and vecuronium.

b) Indications for use (15%)

Neostigmine	Sugammadex
Reversal of non-depolarising neuromuscular blockade once spontaneous recovery has begun; works with both aminosteroid and benzylisoquinolinium blockers.	Reversal of rocuronium or vecuronium; can reverse moderate, deep, or immediate rocuronium block.

c) Dose and dosing considerations (15%)

Feature	Neostigmine	Sugammadex
Dose	0.03–0.07 mg/kg IV; max 5 mg.	2 mg/kg moderate block; 4 mg/kg deep block; 16 mg/kg immediate rocuronium reversal.
Key consideration	Requires spontaneous recovery; ceiling effect. Give with atropine or glycopyrrolate.	Dose by depth of block. Predominantly renal elimination; avoid/limit use in severe renal impairment.

d) Pharmacodynamics and adverse effects (40%)

Feature	Neostigmine	Sugammadex
Neuromuscular effect	↑ ACh at the NMJ → competes with residual blocker and restores transmission.	Rapidly lowers free rocuronium/vecuronium → reversal of block.
Autonomic effects	↑ muscarinic ACh → bradycardia, bronchoconstriction, secretions, GI hypermotility.	No cholinergic effect; no antimuscarinic required.
Neuromuscular adverse effects	Excess dosing can cause weakness / cholinergic crisis; may prolong suxamethonium.	Incomplete or recurrent block if underdosed.
Major other adverse effects	Nausea/vomiting, abdominal cramps, miosis, sweating.	Anaphylaxis, marked bradycardia; interaction with hormonal contraception.
Key practical point	Give with atropine or glycopyrrolate.	Renally cleared; avoid/limit use in severe renal impairment.

Exam focus

Compare rather than write two separate monographs.
Know the key mechanism contrast: ↑ ACh with a ceiling effect versus direct aminosteroid encapsulation.
Know the doses: neostigmine 0.03–0.07 mg/kg; sugammadex 2 / 4 / 16 mg/kg.

Quick reference

Summary

Feature	Neostigmine	Sugammadex
Mechanism	Reversible acetylcholinesterase inhibition → ↑ ACh	Encapsulates rocuronium/vecuronium → removes free blocker
Depth of block	Needs spontaneous recovery; ceiling effect	Moderate/deep/immediate reversal
Dose	0.03–0.07 mg/kg IV; max 5 mg	2 / 4 / 16 mg/kg according to depth
Co-drug	Atropine or glycopyrrolate required	No antimuscarinic required
Main adverse effects	Bradycardia, bronchoconstriction, secretions, GI effects, cholinergic weakness	Anaphylaxis, bradycardia, recurrence/interactions, renal impairment considerations

Past papers

Exam appearances

1 appearance

Exam	Exact exam wording	Candidate success
2026A Q15	Compare and contrast neostigmine and sugammadex using the following headings: a) drug class and mechanism of action (30% of marks), b) indications for use (15% of marks), c) dose and dosing considerations (15% of marks), d) pharmacodynamics and adverse effects (40% of marks).	45.8%