Methadone: applications in pediatric anesthesiology and critical care medicine.

Like morphine, methadone is a pure agonist at the µ opioid receptor. However, in distinction to morphine which has an elimination half-life of 2-3 h, methadone has an elimination half-life of 24-36 h. In addition to its effects at the µ opioid receptor, methadone is an antagonist at the N-methyl-D-aspartate (NMDA) receptor and also inhibits the reuptake of the neurotransmitters, serotonin and norepinephrine, in the central nervous system. Given its long half-life and high oral bioavailability, methadone has had a primary role in the outpatient treatment of patients with a history of opioid abuse or addiction. However, its unique pharmacology and cellular effects make it a valuable agent in the treatment of both acute and chronic pain of various etiologies. The following manuscript reviews the pharmacologic properties of methadone and discusses its clinical applications in the practice of pediatric anesthesiology and pediatric critical care medicine.