Commonly used muscle relaxant therapies for acute low back pain: a review of carisoprodol, cyclobenzaprine hydrochloride, and metaxalone.

Low back pain is a leading reason for primary care visits. Many treatment options are available, but some lack scientific support. The aim of this review was to discuss the etiology of low back pain and the relative risks and benefits of muscle relaxants commonly prescribed for the management of back pain. We searched Intercontinental Marketing Services data for January 2003 through January 2004 to determine the most commonly prescribed agents for the management of musculoskeletal pain. Carisoprodol, cyclobenzaprine hydrochloride, and metaxalone represented >45% of all such prescriptions. Cochrane Library, MEDLINE, and EMBASE databases were searched (time frame: 1960 through January 2004; search terms: back pain, carisoprodol, cyclobenzaprine, metaxalone, muscle relaxants, and pharmacotherapy) and reference lists of identified articles were hand-searched. Three trials of carisoprodol (N = 197) were located in the Cochrane Library database. Two double-blind, randomized, placebo-controlled trials evaluating the safety and efficacy of cyclobenzaprine hydrochloride (N = 1405) were identified in the literature. Three double-blind, placebo-controlled trials were identified for metaxalone (N = 428) in 2 reports. The types of adverse events seen with these agents involved the central nervous system, including drowsiness/sedation, fatigue, and dizziness. However, the efficacy of cyclobenzaprine hydrochloride was shown to be independent of its sedative effects, which were dose related. The potential for abuse with carisoprodol is of growing concern. Analgesic pain management for low back pain due to muscle spasm may be combined with a muscle relaxant. Cyclobenzaprine hydrochloride has the most recent and largest clinical trials demonstrating its benefit, but carisoprodol and metaxalone also appear to be effective. However, carisoprodol's usefulness is mitigated by its potential for abuse.