Abstract. Background. Sexual dysfunction is a frequently overlooked but important side effect of opioid maintenance therapy (OMT) that adversely affects quality of life. This study compared the prevalence, severity, and domain-specific sexual dysfunction in opioid-dependent patients receiving methadone versus buprenorphine maintenance therapy. Methods. In this cross-sectional study, 103 patients undergoing OMT at an outpatient addiction center in Tehran, Iran, were assessed using the International Index of Erectile Function (IIEF) for males and the Female Sexual Function Index (FSFI) for females. Demographic and clinical characteristics were collected. Statistical analyses included chi-square tests, in-dependent t-tests, multivariate regression, and effect size calculations using Cramér’s V. Results. Methadone users reported significantly greater sexual dysfunction than buprenorphine users, particularly in the total IIEF score (p = 0.004, V = 0.434), erectile function (p = 0.027, V = 0.368), and intercourse satisfaction (p < 0.001, V = 0.498). Among methadone users, severe intercourse dissatisfaction was reported by 56.4%, compared to 14.3% of buprenorphine users. Female methadone users experienced more moderate to severe impairment on the FSFI, though this difference was not statistically significant (p = 0.174). Marital status was positively correlated with sexual function scores (IIEF: r = 0.30, p = 0.006; FSFI: r = 0.50, p = 0.045). Conclusions. Methadone is associated with more pronounced sexual dysfunction than buprenorphine, especially regarding erectile function and intercourse satisfaction. These findings emphasize the necessity of integrating sexual health assessment and individualized management into OMT programs to improve treatment adherence and patient quality of life.

Key words: buprenorphine, methadone, opioid dependence, quality of life, sexual dysfunction

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