Fig. 3. Dose-adjusted methadone and 2-ethylidene-1.5-dimethyl-3.3diphenylpyrrolidine (EDDP) enantiomer plasma concentrations after intravenous methadone in all subjects. Solid symbols and lines show R-methadone and R-EDDP, open symbols and dotted lines show S-methadone and S-EDDP. Each data point is the mean ± SD (n = 31). The insets show dose-adjusted methadone and EDDP enantiomer plasma concentrations from 0–12 h, and plasma R/S-methadone concentration ratios.