Injury in an elderly population before and after initiating a skeletal muscle relaxant

Quality guidelines recommend avoidance of skeletal muscle relaxants in patients 65 years and older, but this recommendation is based on expert opinion, not evidence.

To describe an elderly population using skeletal muscle relaxants and compare the incidence of physical injury among these patients before and after initiation of the medication.

This was a retrospective, pre-post cohort analysis, with each patient serving as his/her own control. In a population of elderly patients who purchased a prescription for a skeletal muscle relaxant, the primary outcome was to compare the proportion of patients experiencing an injury in a 60-day period prior to initiating the drug to the proportion experiencing an injury in the 60 days immediately following the purchase date.

Of the 11,875 patients included in the study, 108 (0.9%) experienced an injury during the baseline period and 144 (1.2%) experienced an injury in the 60-day follow-up period (unadjusted OR 1.35; 95% CI 1.05 to 1.75; adjusted OR 1.35; 95% CI 1.01 to 1.81). A total of 333 patients needed to be treated with a skeletal muscle relaxant to result in 1 additional injury. Independent predictors of an injury included a history of an injury in the previous 6 months (OR 3.01; 95% CI 1.54 to 5.88) and older age (OR 1.06; 95% CI 1.04 to 1.09).

The absolute increase in risk of injury in this population using a skeletal muscle relaxant was small but statistically significant. Cautionary use of these medications in the elderly continues to be advisable, but their use in selected patients 65 years and older could be considered if the expected benefits outweigh the small increased risk of injury. More study is needed to quantify the benefits versus risks of these medications in this population.