Medications for opioid use disorder: Predictors of early discontinuation and reduction of overdose risk in US military veterans by medication type.

ABSTRACT

AIM: This study (1) estimated the effect of early discontinuation of medication for opioid use disorder (MOUD) on overdose probability and (2) measured the relationship between patient characteristics and early discontinuation probability for each MOUD type. DESIGN, SETTING AND PARTICIPANTS: This was a retrospective cohort using electronic health record data from the US Veterans Healthcare Administration. Participants were veterans initiating MOUD with buprenorphine (BUP), methadone (MET) or extended-release naltrexone (XR-NTX) from fiscal years 2012-19. A total of 39 284 veterans met eligibility with 22 721 (57.8%) initiating BUP, 12 652 (32.2%) initiating MET and 3911 (10.0%) initiating XR-NTX. MEASUREMENTS Measurements (1) determined whether the veteran experienced an overdose in the 365 days after MOUD initiation (primary) and (2) early discontinuation of MOUD, defined as discontinuation before 180 days (secondary). We assumed that unobserved patient characteristics would jointly influence the probability of discontinuation and overdose. and estimated the joint distribution with a bivariate probit model. FINDINGS: We found that 9.0% of BUP initiators who experienced an overdose above the predicted 3.9% had no veteran-discontinued BUP early; findings for XR-NTX were similar, with 12.2% of initiators overdosing above the predicted 4.5%, but this was statistically inconclusive. We found no relationship between early discontinuation and overdose for MET initiators, probably due to the high risk of both events. The patient characteristics included in our post-estimation exploratory analysis of early discontinuation varied by MOUD type, with between 14 (XR-NTX) and 25 (BUP) tested. The only characteristics with at least one level showing a statistically significant change in probability of early discontinuation for all three MOUD types were geography and prior-year exposure to psychotherapy, although direction and magnitude varied. CONCLUSION: Early discontinuation of buprenorphine, and probably extended-release naltrexone, appears to be associated with a greater probability of experiencing a fatal or non-fatal overdose among US veterans receiving medication for opioid use disorder (MOUD); methadone does not show the same association. There is no consistent set of characteristics among early discontinuers by MOUD type.