mivacurium

Mivacurium is a short-acting, nondepolarizing neuromuscular blocking agent used during anesthesia to facilitate tracheal intubation and provide skeletal muscle relaxation for brief surgical procedures.

Mechanism of action: it acts as a competitive antagonist at nicotinic acetylcholine receptors at the neuromuscular junction, preventing acetylcholine from triggering muscle contraction. It produces flaccid paralysis while leaving consciousness and pain perception unaffected.

Pharmacokinetics: mivacurium is administered intravenously and has a rapid onset, typically 1–2 minutes for adequate relaxation. Its duration of action is short, usually 10–20 minutes, depending on dose and patient factors. It is rapidly hydrolyzed by plasma cholinesterase (pseudocholinesterase) to inactive metabolites, with recovery corresponding to enzyme activity. In individuals with atypical pseudocholinesterase deficiency, paralysis may be markedly prolonged.

Adverse effects: histamine release can cause hypotension and flushing, and at higher doses or in susceptible individuals may provoke tachycardia or bronchospasm. Rare allergic reactions have been reported. Interactions with other agents that affect neuromuscular transmission, such as aminoglycoside antibiotics or certain volatile anesthetics, can potentiate blockade.

Contraindications and cautions: contraindicated in known hypersensitivity to mivacurium. Caution in patients with pseudocholinesterase deficiency, neuromuscular disorders, significant electrolyte disturbances, or cardiovascular instability.

Clinical use: compared with longer-acting nondepolarizing agents, mivacurium offers rapid recovery but carries a higher risk of histamine-related effects and variable duration in atypical cholinesterase states, which has limited its use in some settings.