Trends in opioid analgesic utilisation among people with a history of opioid dependence.

Background: We aimed to characterise opioid analgesic utilisation over a 16-year period among a cohort of people with a history of opioid dependence, comparing rates of use in and out of opioid agonist treatment (OAT).
Methods: Retrospective cohort study in New South Wales, Australia, including 28,891 people with documented opioid dependence initiating opioid analgesics between July 2003 and December 2018. Linked administrative records provided data on prescription dispensings, sociodemographics, clinical characteristics, and OAT. Generalised estimating equation models estimated the incidence and adjusted incidence rate ratios (IRR) comparing periods in and out of OAT for the number of opioid analgesic dispensings (overall, for strong opioids, and the most commonly dispensed opioid types) and the amount dispensed in oral morphine equivalent milligrams (OME).
Results: At initiation, 43.7% of the cohort were enrolled in OAT. The most commonly initiated opioid was codeine (including combinations with paracetamol; 67.8%), and 49.6% of the cohort were dispensed a psychotropic medicine in the previous 90 days. Incidence of all opioid analgesic dispensings was higher during periods out of OAT compared to in OAT (5.8 v. 2.3 dispensings per person-year; IRR 0.39, 95% CI 0.38, 0.41), with findings similar when stratified by type. Being in OAT was associated with a lower OME amount dispensed compared to out of OAT (-57.7%, 95% CI-58.8, -56.7).
Conclusions: People with opioid dependence had high rates of recent psychotropic medicine utilisation and current OAT enrolment at the time of opioid analgesic initiation. OAT was associated with a significant reduction in opioid analgesic dispensing.
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