NMJBlocker

NMJBlocker is a term for agents that inhibit transmission at the neuromuscular junction, producing skeletal muscle paralysis. In clinical practice they facilitate endotracheal intubation and provide muscle relaxation during anesthesia and mechanical ventilation. They are divided into non-depolarizing and depolarizing agents, each with distinct mechanisms and clinical profiles.

Non-depolarizing NMJBlockers are competitive antagonists of nicotinic acetylcholine receptors at the motor endplate. They prevent acetylcholine from triggering action potentials, causing reversible flaccid paralysis. Recovery depends on dissociation of the drug; reversal is achieved with acetylcholinesterase inhibitors.

Depolarizing NMJBlockers activate the nicotinic receptor, causing an initial excitation followed by a prolonged depolarized state in which the endplate cannot respond to further stimuli. This yields rapid, short-lived paralysis as the drug is hydrolyzed.

Onset for intravenous use is typically one to three minutes; duration ranges from minutes for depolarizing agents to longer for many non-depolarizing agents. Pharmacokinetics vary with age, weight, organ function and drug structure. Reversal strategies depend on the blocker class.

Clinical concerns include respiratory and cardiovascular effects, potential histamine release, and muscarinic side effects. Prolonged paralysis may occur with atypical cholinesterase activity or drug interactions; malignant hyperthermia risk is linked to certain depolarizing blockers and triggering anesthetics.

NMJBlockers have a long history in anesthesia, with early agents derived from curare. Modern agents emphasize specific onset and duration profiles and are used in perioperative care to produce muscle relaxation.