Pharmacotherapy in methadone maintenance: Clinical utility of peak-trough blood levels

Objectives: To describe relationships among methadone dose, 3-hour peak and 24-hour trough blood levels, and demography during stable maintenance therapy. Materials and Methods: Participants included 77 men and 3 women, aged 24 to 77. Methadone dose, peak, and trough blood levels covered a 24-hour cycle, obtained during stable, postinduction methadone maintenance. Results: Methadone doses showed moderately strong correlation with 3-hour postdosing "peak" levels, but not with the 24-hour "trough" level. Trough levels were inversely and strongly correlated with the peak-totrough ratio, an index of methadone metabolism. Univariate comparisons revealed that age was correlated moderately and directly with trough level. On regression analyses, older age bore an independent relationship to increased trough level and to slow methadone metabolism. Conclusions: Clinician access to peak and trough levels facilitates safe methadone dosing (including total dose and dose splitting) and precise knowledge regarding rate of methadone metabolism (so that very slow and very rapid metabolizers can receive individualized care).