A retrospective cohort study of medication dispensing at pharmacies: Administration matters!

Abstract

Background: Opioid agonist treatment (OAT) for opioid use disorders may be delivered at treatment clinics or dispensed from pharmacies, however the type of delivery may be associated with different risks and benefits. The aim of the study was to investigate whether dispensing of methadone or buprenorphine at pharmacies during treatment for opioid use disorders was associated with adverse outcomes.

Methods: Retrospective cohort study using a national, linked, population-level data set from Denmark. Patients included were between 18 and 75 years, living in Denmark, and admitted for treatment for opioid use disorders during 2000-2016 (n = 9299). Cox proportional hazards regression was estimated for convictions, non-fatal overdoses, and death, after the first dispensing of either methadone or buprenorphine from a pharmacy after starting treatment.

Findings: Of all patients, 68 % had methadone and 31 % had buprenorphine dispensed at a pharmacy. Compared with the time prior to pharmacy dispension, the risk of criminal convictions increased after having methadone dispensed from a pharmacy (adjusted hazard ratio (aHR) = 1.22, 95 % confidence interval (CI) = 1.16-1.28), non-fatal overdoses (aHR = 1.55, CI 1.41-1.71), and all-cause mortality (aHR = 1.54, CI = 1.43-1.76). After having buprenorphine dispensed at a pharmacy, risk of criminal convictions increased (aHR = 1.08, CI = 1.01-1.16) and non-fatal overdoses (aHR = 1.31, CI = 1.18-1.45), but not all-cause mortality (aHR = 1.07, CI = 0.94-1.23).

Conclusions: For almost all outcomes investigated across medication type, the risk of adverse events increased following a switch from clinic dispension to pharmacy dispension of medications in OAT. Medically responsible and safe provision of OAT may often require more clinical follow-up than what is typically provided when medication is dispensed at pharmacies.

Keywords: Medication-Assisted treatment; Opioid use; Pharmacy; Prescription; Risk factors.