Neuromuscular Blockers Health Article

Definition

Neuromuscular blocking agents are a class of drugs primarily indicated for use as an adjunct to anesthesia. Neuromuscular blocking drugs relax skeletal muscles and induce paralysis.

Purpose

Neuromuscular blockers are indicated for a wide variety of uses in a hospital setting, from surgery to trauma care. In surgery, they are used to prepare patients for intubation before being placed on a ventilator and to suppress the patient's spontaneous breathing once on a ventilator.

Description

Neuromuscular blockers relax skeletal muscle tone by blocking transmission of key neurotransmitters through the neuron receptors at the neuromuscular junction (NMJ). They are divided into two major categories, depolarizing and non-depolarizing neuromuscular blockers, corresponding to the manner in which they exert their therapeutic effect. Depolarizing neuromuscular blocking agents mimic the effects of the neurotransmitter acetylcholine (ACh) and change the interaction between ACh and neuron receptors. Blockade occurs because membranes surrounding the neuromuscular junction become unresponsive to typical ACh-receptor interaction. Non-depolarizing neuromuscular blockers bind to receptors to prevent transmission of impulses through ACh neurotransmitters.

Neuromuscular blockers are primarily used in a clinical or hospital setting. In the United States, they are known by several generic and brand names, including atracurium (Tracurium), cisatracurium (Nimbex), doxacurium (Neuromax), mivacurium (Mivacron), pancuronium (Pavulon), pipecuronium (Arduan), rocuronium (Zemeron), succinylcholine (Anectine), tubocurarine, and vecuronium (Norcuron).

A physician will decide which neuromuscular blocking agent, or combination of neuromuscular blocker and other type of anesthesia, is appropriate for an individual patient. During surgical anesthesia, neuromuscular blockers are administered after the induction of unconsciousness, in order to avoid patient distress at the inability to purposefully move muscles. Neuromuscular blockers can be used on pediatric patients.

Recommended dosage

Neuromuscular blocking agents are most often administered though an intravenous (IV) infusion tube. Typically, the time in which the medicines begin to exert their effects and duration of action are more predictable when neuromuscular blocking agents are administered via IV. Dosages vary depending on the neuromuscular blocking agent used and the duration of action desired. The age, weight, and general health of an individual patient can also affect dosing requirements.

Depolarizing and non-depolarizing agents are grouped together into three categories based on the time in which they begin to exert their anesthetic effects, causing muscle relaxation or paralysis and desensitization, and the duration of those effects (duration of action). Short-acting neuromuscular blockers begin to work within 30 seconds to two-and-a-half minutes and have a typical duration of action ranging from five to twenty minutes. Short-acting agents include mivacurium, rocuronium, and succinylcholine. Intermediate-acting agents exert their effects within two to five minutes and typically last for twenty to sixty minutes. Atracurium, cisatracurium, pancuronium, and vecuronium are intermediate-acting neuromuscular blockers. Long-acting neuromuscular blocking agents take effect within two-and-a-half to six minutes and last as long as 75–100 minutes. Doxacurium, pipecuronium, and tubocurarine are long-acting neuromuscular blocking agents.

The duration of action of any neuromuscular blocking agent can be prolonged by administering smaller supplemental (maintenance) doses via IV following the initial blockade-creating dose.