Muscle relaxants are medicines that block the nerve impulses to the muscles. They sometimes are also referred to as neuromuscular blocking agents. These medicines are often used during anesthesia, but they do not usually affect whether you are awake. They also don't relieve pain. They are given through a vein.
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 belly or chest for surgery in those parts of the body or to relax eye muscles in certain kinds of eye surgery. A muscle relaxant may permit easy movement of joints during bone and joint surgery.
Muscle relaxants are also used to relax the neck and throat and reduce the risk of injury when an endotracheal (ET) tube is inserted. They may also be used to relax the chest muscles when an ET tube is used to help a person breathe (mechanical ventilation).