Nicotinic Receptor Antagonists

Question 1

Vecuronium / Pancuronium
MOA

Answer 1

Reversible competitive antagonism at muscle-type nicotinic receptors. Inhibits binding of ACh to the
receptors at the muscle end-plate. End-plate potential fails to reach the threshold for initiation and
propagation of the action potential along the muscle Fiber. Action reversed by anticholinesterases
(e.g. neostigmine)

Question 2

Vecuronium / Pancuronium
Abs/Distrb/Elim

Answer 2

Given i.v.
Half-life 2–3h.
Substantial renal excretion (duration increased in renal failure).

Question 3

Vecuronium / Pancuronium
Clinical use

Answer 3

In general anaesthesia – aids tracheal intubation, provides muscle relaxation for general surgery and
aids mechanical ventilation

Question 4

Vecuronium / Pancuronium
Adverse effects

Answer 4

Tachycardia (muscarinic antagonist action).

Question 5

Vecuronium / Pancuronium
Special point

Answer 5

Tubocurarine is the archetypal non-depolarizing neuromuscular blocker, but it has more side effects,
such as bronchoconstriction due to histamine release, and is now rarely used.