Opioid agonist therapy take-home levels increased as a result of the COVID-19 pandemic but did not result in a higher incidence of overdose
Opioid agonist therapy (OAT) take-home medication levels increased during the early stages of the COVID-19 pandemic but were not associated with an increased risk of overdose, treatment discontinuation or therapy interruption. This was the main finding by a study undertaken by researchers from the Li Ka Shing Knowledge Institute of St Michael’s Hospital, Toronto, Canada.
Globally, it has been estimated that about 275 million people (5.5% of the world’s population aged 15-64 years) used drugs at least once in 2019, of whom about 62 million people used opioids. Furthermore, there is good evidence from a 2017 systematic review, that retention in methadone and buprenorphine programs is associated with substantial reductions in the risk for all cause and overdose mortality in people dependent on opioids. However, despite these advantages, retention rates within such programs varies considerably and in a 2016 systematic review, it was found that retention rates within randomised controlled trials ranged between 19 and 94% after 3 months and 37 to 91% after 12 months. While there are a number of possible reasons why retention rates vary so much, one qualitative study identified how nearly all of the patients with past or present methadone maintenance treatments, were highly critical of the limited access to take-home doses and consequent need for daily or near daily clinic attendance.
With the arrival of the COVID-19 pandemic, the Canadian team set out to determine whether the increased access to take-home doses of OAT impacted on the level of opioid-related harms such as overdose as well as treatment interruption and discontinuation. The team considered 4 OAT cohorts: those receiving daily methadone; daily buprenorphine/naloxone; weekly dispensed methadone and finally weekly dispensed buprenorphine/naloxone. For comparative purposes, the researchers dichotomised participants into those whose dispensing arrangements remained unchanged and those who were allowed to have a large number of take-home doses. The primary outcomes of interest were fatal or nonfatal opioid overdose, interruption in OAT and OAT discontinuation and all individuals were monitored for 180 days.
Opioid agonist therapy and risk of overdose
Overall, there were 5852 methadone and 662 buprenorphine/naloxone recipients and the median age ranged between 38 and 42 years with 29.1% to 38.2% being women.
Among those prescribed methadone and allowed to take-home more doses, there was a significantly lower risk of opioid overdose (6.9% vs 9.5%/person-year) giving a hazard ratio (HR) of 0.73 (95% CI 0.56 – 0.96), OAT discontinuation (HR = 0.80, 95% CI 0.72 – 0.90) and treatment interruption (HR = 0.80, 95% CI 0.67 – 0.95), compared to those who continued with daily take-outs. Moreover, there was no significant association between the initiation of take-out methadone and the risk of all-cause mortality (HR = 1.16, 95% CI 0.62 – 2.16) or opioid-related death (HR = 1.26, 95% CI 0.48 – 3.33).
Similarly, among buprenorphine/naloxone participants, transitioning from daily to take-home doses was also not associated with opioid overdose risk (HR = 1.86, 95% CI 0.70 – 4.92), treatment discontinuation (HR = 0.91, 95% CI 0.68 – 1.22) or therapy interruption (HR = 0.86, 95% CI 0.52 – 1.41) when compared to those who continued to receive daily doses.
Despite the findings that increased take-home doses of OAT did not lead to an increased risk of opioid overdose, the authors added the caveat to their conclusion that the findings might be due to residual confounding and should be interpreted cautiously.