The use of methadone in cancer pain – a narrative review

Abstract

Methadone is a synthetic opioid, which acts on several receptors, including antagonism to the N-methyl D-Aspartate (NMDA) receptor and inhibitory action on the reuptake of norepinephrine and serotonin, being an important drug in reducing the phenomenon of hyperalgesia related to with the central sensitization process. It plays an important role in complex cancer pain related to its ability to provide multimodal analgesia. It has a long half-life, high oral bioavailability, wide availability of formulations, rapid onset of action and is a safe drug in patients with chronic renal failure. However, this opioid also presents side effects, mediated by opioid and non-opioid receptors, highlighting the risk of sedation, delirium and prolongation of the QT interval. Furthermore, it presents a high risk of accumulation with the administration of repeated doses due to its long half-life and great individual variability. In clinical practice, methadone can be used in different ways: first-line therapy in opioid-naïve patients; 2nd line therapy when rotating an opioid or associated with another opioid at a low dose. Careful monitoring is required when titrating doses and converting other opioids, which means that despite being a versatile drug with numerous advantages, its use on a daily basis is not common, thus requiring greater experience and knowledge on the part of health professionals.