Muscle relaxants: still not very relaxing

Most people — both patients and many professionals — assume that muscle relaxants are effective, especially for injured necks and backs. This does not appear to be a safe assumption.

A new study in the Canadian Journal of Emergency Medical Care compared ibuprofen and a muscle relaxant (cyclobenzaprine or Flexeril) for patients with serious soft-tissue injury in the neck. Groups of about 20 patients received one, the other, or both. Results were statistically identical for all patients. This test showed no benefit to using or adding a muscle relaxant for acute muscle strain in the neck. The study is too small to be powerful, but it certainly shows that there’s no clear advantage to muscle relaxants in a situation where they are often assumed to be an important medication, and the results are consistent with other research results.

The surprise here is not just that muscle relaxants weren’t obviously superior, but that they even performed as well as ibuprofen! Despite the many kinds of muscle relaxants, and their many possible uses, as a class of drug they are remarkably unimpressive in the management of common pain problems. A 2008 physician tutorial in American Family Physician (see See et al — that’s not a typo, the lead author’s name is actually “See”!) nicely sums up the blah state of the evidence:

Skeletal muscle relaxants are widely used in treating musculoskeletal conditions. However, evidence of their effectiveness consists mainly of studies with poor methodologic design. In addition, these drugs have not been proven to be superior to acetaminophen or nonsteroidal anti-inflammatory drugs for low back pain.

And “skeletal muscle relaxants should not be the primary drug class of choice for musculoskeletal conditions.”