Pharmacogenetic study of methadone treatment for heroin addiction: associations between drug-metabolizing gene polymorphisms and treatment efficacy.

Objectives: Opioid dependence is currently one of the most serious problems affecting the social norms and public health system. Methadone maintenance therapy (MMT) is being widely used in treating heroin-dependent patients. The mechanism of methadone metabolism and disposition has been shown to involve cytochrome P450 (CYP450) and P-glycoprotein. The aim of this study was to explore the relationships among genetic polymorphisms, BMI and effective dose of methadone used in MMT within a northern Taiwan cohort.

Methods: One hundred heroin-dependent patients were enrolled in the study. The clinical data gathered included methadone dose, sex and BMI. DNA was collected from the oral swab of the participants to analyze the relevant alleles.

Results: An effective methadone dose correlated with sex, BMI and the presence of ABCB1 2677GG (rs2032582) and CYP2B6 516GG (rs374527). Furthermore, the CYP2B6 516GG homozygote was related to a higher average dose of methadone (GG: 68.50 ± 32.43; GT: 52.28 ± 25.75; TT: 44.44 ± 29.64; P < 0.02), whereas the ABCB1 2677GG homozygote was related to a lower dose (GG: 51.09 ± 20.83; GT: 69.65 ± 37.51; TT: 62.52 ± 30.44; P < 0.05). We examined the predictive effect of polymorphisms combined with sex and BMI on methadone dose by conducting multiple linear regressions. Our data predicted the average dose of methadone in approximately 30% of heroin-dependent patients.

Conclusion: The interactions between genetic polymorphisms and clinical features proved useful in identifying the effective dose of MMT for heroin-dependent patients in Taiwan more precisely.