Patients At Highest Risk of Overdose at Beginning, After End of Methadone Treatment

Patients receiving methadone treatment are at most risk of overdosing during the first 4 weeks of treatment initiation and following the end of treatment, according to a new study.

The study, published in Addiction, evaluated the risk of mortality associated with interruptions in the continuity of methadone maintenance treatment in opioid-dependent individuals attending specialist addiction services.

The study researchers analyzed data from 2899 patients who were prescribed and dispensed methadone in addiction services between January 2010 and December 2015. There was 5 exposure groups: weeks 1 to 4 following transfer between treatment providers, weeks 1 to 4 out of treatment, weeks 5 to 52 out of treatment, weeks 1 to 4 of treatment initiation, and weeks 5 and on of continuous treatment.

Overall, the data showed 154 deaths, 35.7% of which were identified as drug-related poisonings. The results did not show any deaths in the first month following transfer between treatment providers. However, the rate of drug overdose was more than 4 times higher in the month following the end of treatment (ARR 4.04, 95% CI 1.43-11.43, p=0.009) and more than 3 times higher in the first 4 weeks of treatment (ARR 3.4, 95% CI 1.2-9.64, p=0.02).

Additionally, risk of all-cause mortality was highest in the weeks following treatment (ARR 11.78, 95% CI 7.73-17.94, p<0.001), first 4 weeks of treatment (ARR 5.11, 95% CI 2.95-8.83, p<0.001) and weeks 5 to 52 after treatment (ARR 2.04, 95% CI 1.2-3.47, p=0.009). 

“Identifying a higher risk at the beginning and immediately after the end of treatment highlights that retaining patients in treatment for longer periods will save lives,” lead author Dr Gráinne Cousins, senior lecturer at RCSI’s School of Pharmacy and Biomolecular Sciences, said in a news release. “People often cycle in and out of treatment, thereby increasing their exposure to repeated periods of high risk.”

According to Dr Cousins, close monitoring of opioid tolerance before starting treatment and more effective methods at preventing relapse during the induction period may help reduce this risk. Increased patient awareness about the risk of overdose and increasing access to take-home naloxone can also play a role in reducing fatal overdoses during these high-risk periods.

References:

1. Durand L, O’Driscoll D, Boland F, et al. Do interruptions to the continuity of methadone maintenance treatment in specialist addiction settings increase the risk of drug-related poisoning deaths? A retrospective-cohort study. Addiction. 2020. https://doi.org/10.1111/add.15004