Muscle relaxants are not really a class of drugs, but rather a group of different drugs that each has an overall sedative effect on the body. They decrease the muscle tone. Muscle relaxants may be used to treat muscle spasm and pain, hyperreflexia.
There are 2 groups:

1. neuromuscular blockers
2. spasmolytics

Neuromuscular blockers work at the neuromuscular end plate and have no CNS activity. They are often used during surgical procedures and in intensive care to cause paralysis.

Spasmolytics are used to decrease musculoskeletal pain and spasms and to reduce spasticity in a variety of neurological conditions.