Methamphetamine use is increasing in parts of the U.S., yet its impact on treatment for opioid use disorder is relatively unknown.
The study utilized data on adult patients receiving buprenorphine from Washington State Medication Assisted Treatment-Prescription Drug and Opioid Addiction program clinics between November 1, 2015 and April 31, 2018. Past 30-day substance use data were collected at baseline and 6-months, as well as date of program discharge. Cox proportional hazards regression was used to estimate the relative hazards for treatment discharge comparing methamphetamine users at baseline with non-users, adjusting for site, time period, age, gender, race, ethnicity, and education. For a subset of patients with data, we describe the proportion of individuals reporting methamphetamine use at baseline versus 6-months.
The sample included 799 patients, of which 237 (30%) reported using methamphetamine in the past 30 days; of those, 156 (66%) reported 1-10 days of use, 46 (19%) reported 11-20 days of use, and 35 (15%) reported 21-30 days of use. Baseline methamphetamine use was associated with more than twice the relative hazards for discharge in adjusted models (aHR = 2.39; 95% CI: 1.94-2.93). In the sub-sample with data (n = 516), there was an absolute reduction of 15% in methamphetamine use: 135 (26%) reported use at baseline versus 57 (11%) at follow-up.
In summary, this study found that patients who concurrently used methamphetamine were less likely to be retained in buprenorphine treatment compared to non-users. For persons who were retained, however, methamphetamine use decreased over time.f