Methadone for relief of cancer pain: a review of pharmacokinetics, pharmacodynamics, drug interactions and protocols of administration.

Methadone, a synthetic opioid, has unique pharmacodynamics and pharmacokinetics, which contribute to its unique ability to relieve pain unresponsive to other potent opiates and its unique dosing and drug interactions. Several guidelines of administration have been established. Physicians who are involved in pain management should have a fundamental understanding of methadone's unique properties.