Today’s post is a repost of an article I wrote previously about Skeletal Muscle Relaxants (SMRs). Concurrent with this article, I have added a Sample Guideline on prescribing Skeletal Muscle Relaxants to the Guideline Section of JailMedicine.
Personally, I think that skeletal muscle relaxers like cyclobenzaprine, methocarbamol and chlorzoxazone are over prescribed for acute and chronic musculoskeletal pain, both in the outside world but especially in corrections. The main reason for this, I think, is that prescribers misunderstand what muscle relaxers do. Contrary to their name, muscle relaxers do not relax muscles, at least as they are commonly prescribed. Muscle relaxers are sedatives, pure and simple, and should be prescribed with that fact in mind. Instead of telling patients (and ourselves) that “I am prescribing a muscle relaxer for you,” in the interest of full disclosure, we should be saying “I am prescribing a sedative for you.”
Like most of us who sit at a desk, I sit too much hunched over the keyboard with my shoulders rolled forward. This posture overstretches the trapezius and rhomboid muscles. One common consequence of this is to get painful muscle cords in the upper back. When I get these, I can reach back and feel a tight, bunched up knot of muscle fibers between my scapula and spine. These can stick around and be sore for a remarkably long time. So, since the problem here is tight, bunched up muscle cords, wouldn’t carisoprodol (Soma), methocarbamol (Robaxin) or cyclobenzaprine (Flexeril) help to relax them?
You would think that they would—after all; they are listed in the drug classification systems as “skeletal muscle relaxants” and “anti-spasmodics.” You would surely think that if I could measure the amount muscle cord tightness in my back and then took an “antispasmodic muscle relaxer” that the tight area in my back would demonstrably relax.
The answer, though, is “No.” The muscle relaxers would not, in fact, relax that tight muscle cord. In fact, if you look at the medical literature on “muscle relaxers,” whether they actually relax muscles has never even been tested in research! Instead, “muscle relaxers” are always studied as pain relievers, and the setting in which they are most often studied is acute low back pain. The results of this research is interesting:
1.Do “muscle relaxers” relieve acute low back pain more than placebo? (answer: yes).
2. Do “muscle relaxers” work as well for acute low back pain as an NSAID? (answer: No):
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.
3. Is the combination of an NSAID plus a “muscle relaxer” better than an NSAID alone? (answer: no):
“There was no advantage in adding muscle relaxants to NSAIDs for acute LBP.”
What the “muscle relaxers” would do (were I to take them) would be to make me sleepy. This is acknowledged whenever these drugs are described as “centrally acting.” (Code: they relax you by sedating you).
As an example, let’s consider the most commonly prescribed “muscle relaxer” in the United States: Soma (carisoprodol). When it is taken, carisoprodol is immediately metabolized into meprobamate, which is the active component of the drug. Carisoprodol is nothing more than a meprobamate delivery system. Well, meprobamate has an interesting history. Meprobamate was marketed in its own right as an anxiety medication called Miltown. In 1967, the FDA specifically categorized meprobamate as a sedative and listed it as a controlled substance. Production of meprobamate ceased long ago, but carisoprodol (a meprobamate delivery system) has been going strong ever since marketing was switched from being a treatment for anxiety to a “muscle relaxer.”
Carisoprodol is not going to relax my tight cord. It is going to sedate me and make me feel good. The sedation and “feel good” is what makes it popular among patients. The “muscle relaxer” label is what makes it popular among prescribers.
And Soma is not unusual. All of the benzodiazepines do the same thing. In fact, I was taught in my residency that benzodiazepines like Valium were the best muscle relaxers. They also wouldn’t relax my tight back, but they would make me feel good and sleepy! The same is true for all of the “muscle relaxers,” Flexeril, Norflex, Skelaxin and the rest.
Now, I am not saying here never to use “muscle relaxers” (though I personally rarely prescribe them). I am saying that we prescribers should recognize that “muscle relaxers” are sedatives with all of the problems and side effects of any other sedative. We should also recognize that there is very little evidence of their efficacy. So if, despite these two facts, you choose to prescribe “muscle relaxers” in corrections anyway, please follow these two simple rules:
1. Never prescribe muscle relaxers long term for chronic conditions.
2. If you prescribe a “muscle relaxer” for acute low back pain, use them only for a short time. The number usually bandied about is no more than 7 days.