Long-term Muscle Relaxant Use Nearly Triples in the US

Megan Brooks

June 30, 2020

Long-term use of skeletal muscle relaxants nearly tripled in the United States between 2005 and 2016, and these drugs were prescribed disproportionately to older adults, often with an opioid, despite warnings against this potentially dangerous combination, researchers report.

"There are few studies on the short-term efficacy and safety of skeletal muscle relaxants, and almost no data on their long-term effects, so it is very concerning that patients, and particularly older adults, are using these drugs for an extended period of time," Charles E. Leonard, PharmD, said in a statement.

"Providers seem to be reaching for them despite incomplete information on their potential benefits and risks," said Leonard, who is with the Perelman School of Medicine at the University of Pennsylvania in Philadelphia.

The study was published online June 24 in JAMA Network Open.

"Inappropriate" Prescribing

Centrally acting skeletal muscle relaxants (SMRs) are approved for acute musculoskeletal conditions, including spasms and lower back pain, but are often used off label for neuropathic pain, chronic noncancer pain, temporomandibular disorder pain, and numerous conditions not related to pain, the researchers note.

Current recommendations generally limit the duration of use of SMRs to a maximum of 2 to 3 weeks, owing to the risk for side effects. The American Geriatrics Society recommends avoiding SMRs altogether for elderly patients.

"Based on most guidelines, SMRs are normally reserved as second- or third-line therapies. Our findings suggest that prescribers may be reaching for these drugs sooner than that," Leonard said.

The researchers measured national trends in SMR prescribing using data from the National Ambulatory Medical Care Survey for the period 2005 to 2016.

In 2016, there were 30,730,262 office visits in which an SMR was either newly prescribed or was prescribed as ongoing therapy. Most of these visits were made by white women aged 45 to 64 years who were seeking relief of back pain and other musculoskeletal conditions.

During the 12-year study period, office visits with a newly prescribed or continued SMR prescription nearly doubled, from 15.5 million in 2005 to 30.7 million in 2016.

Although office visits with new SMR prescriptions remained stable at around 6 million per year, office visits with continued SMR drug therapy triple, from 8.5 million visits in 2005 to 24.7 million visits in 2016.

In 2016, 67.2% of office visits for continued SMR prescription also involved concomitant therapy with an opioid ― a combination that is associated with serious drug-drug interactions, the data show.

By age, adults older than 65 accounted for 22.2% of visits in which an SMR was prescribed in 2016, although this group made up only 14.5% of the US population.

SMR prescriptions that were considered "potentially inappropriate" in this population roughly doubled, from 2.2 million in 2005 to 4.3 million in 2016, the researchers found.

"Given the findings of this cross-sectional study, efforts to limit the long-term use of SMRs may be needed, especially for older adults, similar to efforts used to limit the long-term use of opioids and benzodiazepines," the investigators conclude.

The study was supported by funding from the National Institutes of Health. Leonard serves on the executive committee of the University of Pennsylvania's Center for Pharmacoepidemiology Research and Training, which receives funding for education from Pfizer. He is also a special government employee of the US Food and Drug Administration.

JAMA Netw Open. Published online June 24, 2020. Full text

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