Wolff and Hay reported an equation correlating the daily dose of methadone with the trough plasma concentration at steady state.
Patient selection: therapy with methadone
Parameters:
(1) total daily methadone dose in mg
(2) body weight in kilograms
methadone in mg per kg =
= (daily dose in mg) / (body weight in kilograms)
plasma concentration of methadone in mg/L =
= (0.263 * (methadone dose in mg per kg)) + 0.002
This is rewritten in Fenske et al as:
plasma trough concentration in ng/mL =
= 263 * (daily dose in mg) / (body weight in kilograms)
