Muscle Relaxants for Low Back Pain

The term "muscle relaxants" is very broad and includes a wide range of drugs with different indications and mechanisms of action. Muscle relaxants are one of the many treatments used in the management of low back pain. About thirty-five percent of patients visiting a physician for low back pain are prescribed muscle relaxants.

Muscle relaxants are one of the many treatments used in the management of low back pain. About thirty-five percent of patients visiting a physician for low back pain are prescribed muscle relaxants.

For acute low back pain, muscle relaxants improve pain, muscle tension, and mobility more effectively than a placebo does. For chronic low back pain, muscle relaxants may relieve pain and lead to overall improvement. However, side effects are common.

The term "muscle relaxants" is very broad and includes a wide range of drugs with different indications and mechanisms of action. Muscle relaxants can be divided into two main categories: antispasmodic and antispasticity medications.

Antispasmodics are used to decrease muscle spasm associated with painful conditions such as back pain. Antispasmodics can be subclassified into benzodiazepines and nonbenzodiazepines. Benzodiazepines (e.g., alprazolam, diazepam, tetrazepam) are used as anxiolytics, sedatives, hypnotics, anticonvulsants, and skeletal muscle relaxants.

Non-benzodiazepines include a variety of drugs that can act at the brain stem or spinal cord level. The mechanisms of action with the central nervous system are still not completely understood.

Carisoprodol and metaxalone have moderate antispasmodic effects and are mildly sedative. Carisoprodol blocks interneuronal activity in the descending reticular formation and spinal cord. Carisoprodol is metabolized to meprobamate. Meprobamate was introduced as an anti-anxiety agent in 1955 and is prescribed primarily to treat anxiety, tension, and associated muscle spasms. Its onset and duration of action are similar to the intermediate-acting barbiturates. Excessive use can result in psychological and physical dependence.

Cyclobenzaprine is structurally similar to the tricyclic antidepressants; however, it has strong side effects such as sedation. It is currently believed that cyclobenzaprine acts in the brain stem rather than at the spinal cord level. Cyclobenzaprine has anticholinergic activity (which is responsible for some side effects such as dry mouth).

The use of muscle relaxants for low back pain continues to be a source of controversy among physicians, mainly because of their side effects. In addition to sedation, potential side effects include drowsiness, headache, blurred vision, nausea, and vomiting. Potential for abuse and dependency has also great drawback. Some guidelines recommend muscle relaxants alone or in combination with NSAIDs as optional, others clearly do not recommend using these drugs. Despite this controversy, 91% of doctors report using muscle relaxants even if they are conditionally discouraged by guidelines.