Treatment with injectable hydromorphone: Comparing retention in double blind and open label treatment periods

In a double-blind, non-inferiority randomized controlled trial injectable hydromorphone, a licensed short acting opioid analgesic, was shown to be as effective as diacetylmorphine for the treatment of severe opioid use disorder. An appropriate question is whether hydromorphone offered open-label can attract and retain patients.

This is a retrospective study, using daily prescription data from the Crosstown Clinic in Vancouver, Canada. Treatment retention among participants who had the opportunity to receive open-label injectable hydromorphone for at least 90 consecutive days (n = 108) before having the choice of receiving open-label diacetylmorphine, was compared to their retention outcomes with double-blind injectable opioid agonist treatment (iOAT). McNemar tests analyzed differences in proportions; a conditional logistic model estimated exact odds ratios; Pairwise t-tests analyzed differences in total number of treatment days; and Kaplan-Meier curves and clustered log-rank tests compared time to first 30 continuous days without injectable treatment.

A total of 74 participants (68.5%) were retained in both open-label hydromorphone and double-blind iOAT. Open-label hydromorphone was not significantly associated with lower retention (OR = 0.5; 95% CI: 0.2, 1.1; p = .10). Participants attended a mean of 84.4 (SD = 15.8) days of iOAT in the trial and 80.5 (SD = 22.0) days in open-label hydromorphone (mean difference of -3.9; 95% CI = -8.9, 1.1). Kaplan-Meier curves and log-rank tests were not statistically significant.

As treatment with injectable hydromorphone expands across Canada, our study contributes in a unique manner by providing evidence that the high retention rates observed during the clinical trial were maintained when participants started open-label hydromorphone.