The pharmacology of methadone makes it a very useful drug for treating opioid dependence. The advantageous features include the fact that methadone:
- is taken orally, which avoids risks associated with injection drug use
- has a long half-life, which means only a single daily dose is needed
- accumulates in the body, which means a steady blood level is achieved easily
- effectively suppresses opioid withdrawal symptoms, which increases comfort/compliance among clients/patients
- develops cross-tolerance (or blockades) to the effects of illicit opioid use, which decreases use of illicit opioids during maintenance
- has no serious long-term side effects when used on a long-term basis (1)
As with any drug, many factors affect the rate at which methadone is metabolized; according to Blum (as cited in Ward et al., 1998h, 207) these include individual differences in metabolic rate, excretion rate, physiological status [e.g., pregnancy], pathological status, and consumption of other drugs.
According to Leshner (1999), "The commonly held belief that methadone....[is] simply [a] substitute for heroin is wrong. Although this medication is a µ-opioid agonist, it's pharmacological and pharmacodynamic properties are quite different from heroin. Instead of destabilizing the individual, as heroin does, methadone....stabilize[s] the patient and facilitate[s] a return to productive functioning."
(1) Novick et al. as cited by Ward et al., 1998h, 207; Walsh & Strain, 1999, 50-51.