"Levomethadyl is a synthetic µ-opioid receptor agonist that is commercially available in a liquid suspension. It is rapidly absorbed from the gastrointestinal tract, although its oral bioavailability is somewhat lower than that of methadone.87 Because of these properties, the opioid effect of levomethadyl is somewhat slower in onset than that of methadone (90 minutes), but it has a much longer duration of action (48-72 hours) and is therefore able to be dispensed 3 times per week."


Mori J. Krantz, MD; Philip S. Mehler, MD, "Treating Opioid Dependence: Growing Implications for Primary Care," Archives of Internal Medicine, (Chicago, IL: American Medical Association, February 2004), Vol. 164, p. 280.