(309) Examining the impact of benzodiazepine formulary restrictions on benzodiazepine-related harms in a Medicaid population, 2004-2016

Background: Benzodiazepine use is associated with an increased rate of fall/fracture injuries, as well as overdoses among those with concomitant opioid use. From 2006 to 2014, benzodiazepine prescriptions were excluded from reimbursement in Tennessee Medicaid (TennCare), providing an opportunity to measure the impact of benzodiazepine-related formulary changes on the rate of benzodiazepine-related harms.

Objectives: To test the hypothesis that the benzodiazepine formulary exclusion in 2006 and the subsequent re-inclusion of benzodiazepines in 2014 impacted the rate of falls, fractures, and overdoses among TennCare patients with indications for benzodiazepine use compared to those without indications.

Methods: We used TennCare claims data (2004-2016) to identify a retrospective cohort of adult patients continuously enrolled in TennCare with and without indications for benzodiazepine use (anxiety disorders, seizures, post-traumatic stress disorder, muscle spasms, neuropathic pain). Patients with indications entered the cohort on earliest date of the indication diagnosis with no evidence of an outcome in the prior 6 months. Patients without indications entered the cohort on the earliest encounter date with no evidence of an outcome or indication in the prior 6 months. Follow up continued until the earliest of: TennCare ineligibility, the outcome (fall/fracture injury, overdose), death, end of study, or benzodiazepine indication diagnosis (control population only). We used a difference-in-differences (DiD) approach with separate linear regression models to determine the impact of the exclusion (2006-07 vs. 2004-05) and subsequent reintroduction (2014-2016 vs. 2011-2013) of benzodiazepines to the formulary among those with indications for benzodiazepines use.

Results: We identified 401,764 and 1,394,426 patients with and without benzodiazepine indications, respectively. The prevalence of fall/fracture-related injuries and overdose was higher among patients with indications (23.3% and 1.2%, respectively) compared to those without (10.2% and 0.2%). DiD analyses identified a significant reduction in fall/fracture-related injury rates associated with the exclusion [-2.15 per 100 person-years (py) (95%CI:-3.06, -1.24) and subsequent reintroduction of benzodiazepines to the formulary [-2.9 per 100 py (95%CI:-3.25, -2.59). The exclusion was associated with a reduction in overdoses [-0.20 per 100 py (95%CI:-0.30, -0.10)], though no change was observed after reintroduction.

Conclusions: The exclusion and subsequent reintroduction of benzodiazepines to the formulary were both associated with a reduction in fall/fracture injuries, whereas the reintroduction of benzodiazepines was not associated with an increase in overdoses.