Methadone against cancer: Lost in translation

Recently, the opioid analgesic d , l ‐methadone has gained much attention as a potential antineoplastic compound, considerably triggered through lay press and media. In consequence, physicians and pharmacists are currently confronted with numerous patients willing to use d , l ‐methadone against their malignancies. Well‐performed in vitro and in vivo models have in fact shown pro‐apoptotic effects of d , l ‐methadone or other opioids, but also proliferation‐stimulating properties. Moreover, the mechanisms of proposed opioid‐stimulated apoptosis are incompletely described or contradicting. Finally, the receptors mostly responsible for induction of apoptosis by d , l ‐methadone remain unclear as contributions of both µ‐opioid receptors, Fas cell death receptors, toll‐like receptors, N ‐Methyl‐ d ‐aspartate receptors and opioid growth factor receptors were suggested. Such ambiguity prevents rational application of d , l ‐methadone or patient stratification to enhance beneficial antineoplastic effects. From a clinical point of view, d , l ‐methadone and other opioids might in fact prolong survival, but such effects likely originate from their analgesic and neuro‐psychotropic properties and, thus, improvements of quality of life. Crucial obstacles to the administration of d , l ‐methadone are incomplete knowledge about its systemic disposition, highly variable pharmacokinetics, profound drug–drug‐ or drug–disease interaction and QT‐prolongation potential. This article summarizes and rates the pharmacological basis of d , l ‐methadone as an antineoplastic agent and puts its administration in clinical oncology into perspective. Despite enthralling experimental findings about d , l ‐methadone‐mediated apoptosis in cancerous cells or tissues, clinicians should realize the current lack of evidence for the use of d , l ‐methadone as an antineoplastic agent. Its administration against cancer pain is, however, tenable, albeit restricted to certain clinical situations.