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Methadone — Onset and Duration of Effect

From: Chapter 3: The Fundamentals of Methadone Maintenance Treatment, in Methadone Maintenance: A Counsellor's Guide to Treatment (© 2003).

Methadone is well and quickly absorbed from the gastrointestinal tract into the bloodstream. It begins to take effect in about 30 minutes. The half-life of methadone (the time for blood levels to drop to 50 per cent of the peak concentration) is about 12 to 18 hours for the first dose and about 13 to 47 hours for the second and third days' doses (Preston et al., 1996). The effects of methadone last about 24 to 36 hours.