[61] Like numerous other cardiotoxic drugs, methadone blocks the hERG K+ channel. The two enantiomers of methadone inhibit hERG channels with diverse potency. Dextromethadone, which can be a lot less powerful as an opioid, is much more potent at blocking the hERG channel with an IC50 of ~12 ?M. Levomethadone has a lower affinity, with an IC50 of ~2