Baclofen, tizanidine linked with increased injury risk in older adults
The two skeletal muscle relaxants were associated with an increased risk of fractures, falls, and other injuries but are not included in the Beers Criteria of potentially inappropriate medications for older adults.
Older adults prescribed baclofen or tizanidine were at an increased risk of injury compared with those prescribed cyclobenzaprine, a retrospective study found.
Researchers performed a retrospective cohort study to compare injury events among three skeletal muscle relaxants: baclofen and tizanidine, which are not listed in the American Geriatrics Society (AGS)'s Beers Criteria as medications to avoid among older adults, and cyclobenzaprine, which is. Data from 87,896 patients ages 65 to 99 years who were receiving care from Kaiser Permanente Southern California were included. All participants were dispensed baclofen (54.8%), tizanidine (6.3%), or cyclobenzaprine (38.9%) between January 2008 and December 2018. The definition of serious injuries included fracture, fall leading to fracture, brain injury, and dislocation injury. Findings were published by the Journal of the American Geriatrics Society on Sept.13.
Of 118,426 study medication episodes, 67,631 (57.1%) were associated with baclofen, 8,074 (6.8%) with tizanidine, and 42,721 (36.1%) with cyclobenzaprine. Risk for the composite injury outcome was 69% greater with baclofen (adjusted hazard ratio, 1.69; 95% CI, 1.51 to 1.88) and 34% higher with tizanidine (adjusted hazard ratio, 1.34; 95% CI, 1.11 to 1.62) compared with cyclobenzaprine. Both baclofen and tizanidine demonstrated lower injury-free probabilities over time when compared with cyclobenzaprine, indicating worse outcomes. Baclofen had a lower injury-free probability than tizanidine, which in turn had a lower injury-free probability than cyclobenzaprine. History of falls, kidney failure, Parkinson's disease, and concomitant use of antidepressants were all significantly associated with an increased risk of injury.
Limitations of the study include the risk of residual confounding and lack of assessment of medication dosage or duration.
“Our findings indicate that baclofen and tizanidine do not represent safer alternatives to cyclobenzaprine for use in older adult patients with musculoskeletal complaints and should be considered for inclusion in future iterations of the AGS Beers Criteria and other guidance publications,” the authors concluded.