The Pharmacokinetics of Methadone Following Co‐Administration with a Lamivudine/Zidovudine Combination Tablet in Opiate‐Dependent Subjects

Methadone pharmacokinetics were determined in an open‐label, within subject study in 16 methadone‐maintained, non‐HIV‐infected subjects prior to and following administration of one lamivudine 150‐mg/zidovudine 300‐mgcombi‐nation tablet to determine whether this antiretroviral therapy alters methadone serum concentrations. No significant differences in the mean are aunder the serum concentration‐time curve (AUC 0‐2 4h; 8753 ± 4280 vs. 8641 ± 4431 μg‐h/L), oralclearance(CL/F;9.9± 4.9vs.10.3 ± 5.5 L/h), oral volume of distribution (Vd/F; 647 ± 465 vs. 481 ± 305 L), maximum serum concentration (C max ; 514 ± 223 vs. 5510 ± 237 μg/L), or terminal elimination half‐life (t l/2 ; 55.3 ± 61.0 vs. 35.0 ± 17.5 h) were detected. These results suggest that methadone dose change is not likely to be necessary for patients treated with lamivudine/zidovudine combination pharmacotherapy.