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METHADONE PLASMA LEVELS IN HEROIN ADDICT PATIENTS DURING SUBSTITUTION THERAPY

ROBERT DANIEL VASILE¹, DANIELA BACONI^1*, CRISTINA HUDIŢĂ², MARIA BÂRCĂ¹, CRISTIAN BĂLĂLĂU³, ANNE-MARIE CIOBANU¹

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Opiates, especially heroin, continue to be the main problem in terms of drug abuse worldwide, as reveal the statistics for the treatment demand. In general, current concerns in the field of diagnosis and treatment of heroin addiction are materialized both in assessing the prevalence and patterns of problem drug use and analytical diagnosis of the consumption, overdoses treatment and establishment the methadone substitution treatment procedures. During the substitution treatment with methadone, it is noticed the need for therapeutic intervention following a well-established treatment plan, correlation, coordinating and adapting the treatment to the specific particularities of each patient. This study aimed the quantification of methadone in plasma of the patients during methadone substitution treatment to assess the possible relationship with methadone doses. The patients selected for the study were long-term heroin addicts (n = 28) volunteering for substitution therapy with methadone (a medium dose of about 60 mg/day), 20 – 43 years old, monitored at the Centre for Evaluation and Treatment of Addictions for Young People "St. Stelian" Bucharest, Romania. Methadone plasma concentrations were determined by a GC-MS method using diphenylamine as internal standard. A large distribution of methadone plasma levels was registered, with an average plasma methadone levels of 303.35 ± 140.33 ng/mL (range 123 – 808 ng/mL); the results are consistent with other studies indicating that plasma methadone levels between 150 and 600 ng/mL are required to counter for the craving effect of opioid addicts. In addition, a positive significant correlation between methadone doses and the plasma levels has been shown. The study suggests that monitoring methadone substitution therapy by analytical methods is useful in assessing compliance and detecting patients with extra-consumption of methadone; also it contributes significantly to avoiding the relapse in drug use and in occasional heroin consumption.