[sixty one] Like numerous other cardiotoxic drugs, methadone blocks the hERG K+ channel. The 2 enantiomers of methadone inhibit hERG channels with unique potency. Dextromethadone, that is fewer potent being an opioid, is more potent at blocking the hERG channel with an IC50 of ~12 ?M. Levomethadone incorporates a lower affinity, with an IC50 of ~29