Impact of recent methamphetamine use on treatment outcomes amongst individuals initiating medications for opioid use disorders in rural treatment settings: a one-year retrospective cohort study

Introduction: Rates of methamphetamine use in rural areas of the United States have been steadily increasing, particularly among individuals who are already struggling with opioid use disorder. Despite this alarming trend, there remains a significant gap in our understanding of how methamphetamine use affects treatment response for those undergoing medications for opioid use disorder (MOUD). This study aimed to explore the predictive role of methamphetamine urinalysis results at intake on treatment retention and opioid and methamphetamine use over time amongst individuals seeking MOUD treatment in four clinics located in rural areas. The study was conducted across four clinics situated in rural areas, where access to addiction treatment services is known to be limited.
Methods: Clinical data collection for this study occurred between January 2019 and December 2019. As such, a substantial number of participants were enrolled from patients initiating treatment in 2019 in four clinics located in rural Oregon were extracted. Data included intake demographics, attendance, and monthly opioid and methamphetamine urinalysis (UA) results over a one-year period. Our primary outcomes were opioid and methamphetamine use, and treatment retention over a 12-month period. Objective verification of opioid and methamphetamine use was determined using UA results collected once per month. Treatment retention was determined considering the number of days elapsed from treatment intake to treatment dropout.  Generalized estimating equations were used to compare methamphetamine and opioid use over time while Kaplan-Maier survival analysis was used to compare treatment retention by methamphetamine urinalysis result at intake.
Results: A total of 554 patients enrolled at one of these four rural MOUD clinics, of which 277 (50%) submitted a negative methamphetamine and 277 (50%) submitted a positive methamphetamine UA at intake. In terms of demographics, our sample was comprised of mostly White individuals (89.5%), half of them male (54.5%), with a mean age of 36.8 years (SD= 10.8). A third were unemployed (32.3%), a quarter reported to have legal problems (26.2%), and 5% of them were currently homeless. When compared to those testing negative for methamphetamine, patients initiating treatment with a positive methamphetamine UA were more likely to be unemployed (36.5% vs 28.2%; p=0.048) and to submit a positive opioid UA at intake (88.4% vs 45.8%; p<0.01). A negative methamphetamine urinalysis at intake was associated with fewer positive methamphetamine urinalysis over time (p=0.02) but was not associated with better treatment response for opioid use over time (p=0.84) nor treatment retention (p=0.51).
Conclusions: While patients initiating MOUD with a negative methamphetamine urinalysis had higher rates of methamphetamine abstinence over time, methamphetamine urinalysis results at intake did not predict worse treatment outcomes in terms of opioid use and treatment retention for patients initiating MOUD in rural areas. Our findings highlight demographic and profile differences between patients who use methamphetamine in MOUD rural settings while revealing significant gaps in the existing knowledge regarding the effects of methamphetamine use on MOUD treatment response. Such findings underscore a critical need for further research to be conducted specifically among rural populations seeking MOUD treatment.
Keywords: medication-assisted treatment, medications for opioid use disorder, methamphetamine use disorder, opioid use disorder, rural.