Correlation between high methadone dose and methadone blood level in methadone maintenance treatment patients

Methadone dosage has been widely related to the degree of enduring opiate use and polyabuse while on methadone, lower dosages favouring partial rather than complete response and a worse outcome. Up to certain threshold, methadone blood levels seem to be directly related to oral dosages, thus supporting the clinical evidence of a methadone-induced, dose-dependent remission of addictive behaviour through a serological marker. In order to assess the clinical meaning of methadone blood levels, and its relationship to oral dosages, we performed an evaluation of 114 methadone treated subjects, who were stable on methadone dosages ranging from 40 to 290 mg (mean 171.7±50.8 mg). Lower methadone dosages correspond to lower blood levels and a higher rate of opiate abuse while on treatment. Non-opiate substance abuse characterized patients on higher methadone dosages, whose methadone blood levels were in fact higher. Cocaine abusers had higher methadone dose regardless of concurrent opioid abuse, while benzodiazepine abuse plays a role in respect to dosage only in those who do not abuse opioids. Blood testing also showed an inverse relationship between methadone dose and blood sodium, which warrants further investigation.