US FDA issues warning on methadone toxicity

The US Food and Drug Administration has reviewed reports of death and life-threatening side effects such as slowed or stopped breathing, and dangerous changes in heart beat, in patients receiving methadone. The agency warns that serious side effects may occur because methadone can build up in the body to a toxic level if it is taken too often, if the amount taken is too high, or if it is taken with certain other medicines or supplements. It advises that physicians prescribing methadone should be familiar with its toxicities and unique pharmacologic properties, which includes an elimination half-life (8-59 hours) longer than its duration of analgesic action (4-8 hours).