Dose, Plasma Level, and Treatment Outcome Among Methadone Patients in Shanghai, China
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The purpose of this study was to investigate the blood levels of methadone in participants receiving methadone for the treatment of opioid dependence. After stabilization on methadone for four weeks, blood samples from 95 participants were collected between treatment weeks 4 and 12, before and after receiving doses of methadone, and its blood levels were measured. A multiple linear regression model was used to examine the association between methadone blood levels and the outcomes of methadone maintenance treatment (MMT). Outcome differences between participants who had high (≥2) or low (<2) peak-to-trough ratios were also compared using an independent sample t-test. The blood level of methadone was not correlated with the clinical outcome of MMT with the moderate range of doses given. However, the retention of patients who had a free peak-to-trough ratio >2 was significantly poorer than those whose ratio was <2. Thus, monitoring plasma methadone levels is unlikely to be effective for guiding dosing decisions in situations where compliance with MMT is already very high or when the methadone dose is no longer the dominant factor in determining the clinical outcome. However, monitoring plasma methadone levels is still helpful for guiding the dosage for patients with a rapid metabolism.
KeywordsMethadone Plasma level Treatment outcome Metabolism
This work was supported by the Research Project of Shanghai Municipal Health and Family Planning Commission, China (2013SY011 and 2014ZYJB0002), the National Natural Science Foundation of China (81271468), Doctoral Supervisor Funding from the Ministry of Education of China (20120073110089), and Research Funding from Shanghai Key Laboratory of Severe Mental illness, China (13dz2260500). We thank the patients and staff of the four Shanghai MMT clinics who participated in this study.
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