Safety of baclofen versus tizanidine for older adults with musculoskeletal pain.

BACKGROUND: Baclofen and tizanidine are both muscle relaxants that carry the risk for neuropsychiatric events in older adults but there is a lack of data directly comparing their safety. This study aimed to investigate the relative risk between these two medications in causing injury and delirium in older adults. METHODS: This was a retrospective cohort study that was completed in an integrated healthcare system in the United States and included patients aged 65 years or older who started baclofen or tizanidine for the treatment of musculoskeletal pain from January 2016 through December 2018. Outcomes included new incidence of injury (concussion, contusion, dislocation, fall, fracture, or other injuries) and delirium. The cohort was followed from the initiation of therapy until the first occurrence of any of the following events: end of the index drug exposure, end of health plan membership, death, or the study end date of December 31st, 2019. Descriptive statistics were used to compare baseline patient characteristics between baclofen and tizanidine treatment groups. Cox proportional hazards model was used to calculate adjusted hazard ratios (HRs) with 95% confidence intervals. RESULTS: The final study cohort included 12,101 and 6,027 older adults in the baclofen and tizanidine group respectively (mean age 72.2 ± 6.2 years old, 59% female). Older adults newly started on baclofen had a greater risk of injury (HR = 1.54, 95% CI = 1.21-1.96, P = < 0.001) and delirium (HR = 3.33, 95% CI = 2.11-5.26, p = <0.001) compared to those started on tizanidine. CONCLUSION: The results of this study suggest that baclofen is associated with higher incidences of injury and delirium compared to tizanidine when used for the treatment of musculoskeletal pain. Future studies should investigate if these risks are dose-related and include a comparison group not exposed to either drug.

Refining the Definition of Polypharmacy and Its Link to Disability in Older Adults: Conceptualizing Necessary Polypharmacy, Unnecessary Polypharmacy, and Polypharmacy of Unclear Benefit.

The term polypharmacy in older adults is generally used in a pejorative context in the medical literature. Because of its link to geriatric syndromes and disability, the avoidance of polypharmacy is usually recommended in older adults as a strategy to optimize functional status. However, there are many polypharmacy regimens based on high-quality trials that clearly reduce the risk of disability in older adults. Other guidelines for older adults recommend the use of additional medications that may or may not be evidence based and that may or may not reduce disability. Therefore, we propose that, in the geriatric literature, polypharmacy now be categorized as "necessary polypharmacy," "unnecessary polypharmacy," or "polypharmacy of unclear benefit." In this article, we discuss the 3 categories of polypharmacy and give examples on each polypharmacy regimen and its potential relationship to disability in older adults.