Pancuronium Bromide - Mechanism of Action

Mechanism of Action

Pancuronium is a typical non-depolarizing curare-mimetic muscle relaxant. It acts as a competitive acetylcholine antagonist on neuromuscular junctions, displacing acetylcholine (hence competitive) from its post-synaptic nicotinic acetylcholine receptors. It is (unlike suxamethonium) a non-depolarizing agent, which means that it causes no spontaneous depolarizations upon association with the nicotinic receptor in neuromuscular junction, thus producing no muscle fasciculations upon administration. Despite being a steroid, pancuronium has no hormonal activity. It exerts slight vagolytic activity (i.e. diminishing activity of the vagus nerve) and no ganglioplegic (i.e. blocking ganglions) activity. Pancuronium is a very potent muscle relaxant/curaremimetic. The ED95 (i.e. a dose causing muscle relaxation suitable for intubation in 95% of the population) is only 60 µg/kg body weight administered intravenously. Muscle relaxation suitable for intubation sets in about 90–120 seconds after administration of the drug. Full muscle paralysis for major surgery is achieved about 2–4 minutes after application. Clinical effects (muscle activity lower than 25% of physiological) last for about 100 minutes. The time needed for full (over 90% muscle activity) recovery after single administration is about 120–180 minutes in healthy adults, but can be protracted to more hours in poor health subjects and when concomitantly administered with other long-acting anesthetics (e.g., some opioids, barbiturates, inhalation anesthetics). The effects of pancuronium can be at least partially reversed by anticholinesterasics, such as neostigmine, pyridostigmine, and edrophonium.