Ansermot et al1 have suggested the possibility that (R)-methadone can be substituted for (R,S)-methadone in clinical practice to decrease methadone-induced prolongation of corrected QT (QTc) intervals, thereby lowering the risk of torsades de pointes. Multiple observations indicate that this recommendation should only be considered after exploring the possibility of a relationship between QTc intervals and testosterone levels in men receiving methadone.
Daniell HW. Does Methadone Prolong QTc Intervals by Depleting Testosterone Levels?. Arch Intern Med. 2010;170(15):1407–1408. doi:10.1001/archinternmed.2010.282