has a slow metabolism
and very high fat solubility, making it longer lasting than morphine-based drugs. Methadone has a typical elimination half-life of 15 to 60 hours with a mean of around 22. The drug is eliminated in even after this time. However, metabolism rates vary greatly between individuals, ranging from as few as 4 hours to as many as 130 hours,or even 190 hours.This variability is apparently due to genetic variability between individuals.