Evaluating the effect of methadone dose on quality of life among people receiving medications for opioid use disorder

Opioid use disorder is associated with poor health-related quality of life (HRQoL). Although methadone maintenance programs improve patient’s stability, the dosage associated with optimal quality of life remains controversial. The SF-6D captures key mental health-related dimensions of quality of life and represents an appropriate preference-based measure for this population dealing with substantial psychosocial burden. In this study, we applied US valuation sets to extract SF-6D scores in the population receiving methadone and focused on evaluating the effect of methadone dose on quality of life through a causal inference method. Baseline data from a completed randomized clinical trial called bio-behavioral Community-Friendly Health Recovery Program (CHRP-BB) was used. CHRP-BB targeted 237 individuals receiving medications for opioid use disorder in New Haven, Connecticut. SF-36 version 1 responses were collected and converted into SF-6D utility scores using the U.S. population valuation set. Association between sociobehavioral factors with SF-6D scores were assessed through parametric and nonparametric tests, correlation analysis, and linear and beta regression modeling. Inverse probability weighting with regression adjustment (IPWRA) was applied with two predefined binary and multinomial treatment models to investigate the average treatment effects (ATE) of methadone dose on HRQoL. Covariate balance was checked using pairwise standardized mean difference. Mean HRQoL was 0.784 (95% CI: 0.778–0.790). Older age was significantly associated with lower SF-6D scores ( p = 0.0165), while neurocognitive impairment showed a negative but non-significant association ( p = 0.053). In binary treatment model, methadone doses ≤ 90 mg were associated with lower SF-6D scores compared with higher doses (ATE = − 0.013, p = 0.040). In multinomial model, compared with doses < 60 mg, methadone doses of 90–120 mg and > 120 mg were associated with significantly higher SF-6D scores (ATE = 0.022, p = 0.005; and ATE = 0.020, p = 0.025, respectively). Increasing methadone dose is associated with higher SF-6D scores after covariate balance. Although higher methadone doses were associated with better quality of life, rigorous causal research is still needed to determine the optimal dosing strategy. These results could be used for cost-effectiveness analysis of opioid agonist therapy programs across the US. CHRP-BB was registered at ClinicalTrials.gov (NCT03282890) on 14 September 2017.