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Muscle relaxants are medicines that block transmission of nerve impulses to the muscles. They sometimes are also referred to as neuromuscular blocking agents. These medicines are often used during anesthesia but do not usually affect consciousness and do not provide pain relief (analgesia). They are given through a vein (intravenously).

Some general anesthetics also cause some muscle relaxation. But in many cases a second medicine will be used during anesthesia to relax muscle tone throughout your body or to relax specific muscles. For example, a muscle relaxant may be used to relax muscles in the abdomen or chest for surgery in those parts of the body, relax eye muscles in certain kinds of eye surgery, or permit easy movement of joints during bone and joint surgery.

Muscle relaxants are also used routinely during the insertion of an endotracheal (ET) tube to relax the muscles in the neck and throat, which reduces the risk of injury. They may also be used to relax the chest muscles when an endotracheal tube is used to help a person breathe (mechanical ventilation).

Muscle relaxants commonly used during anesthesia include rocuronium, succinylcholine, and vecuronium.