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Stereoselective block of hERG channel by (S)-methadone and QT interval prolongation in CYP2B6 slow metabolizers

Eap, C B.
Crettol, S.
Rougier, J-S.
Schläpfer, J.
Déglon, J-J.
Besson, J.
Croquette-Krokar, M.
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Published in Clinical Pharmacology and Therapeutics. 2007, vol. 81, no. 5, p. 719-28
Abstract Methadone inhibits the cardiac potassium channel hERG and can cause a prolonged QT interval. Methadone is chiral but its therapeutic activity is mainly due to (R)-methadone. Whole-cell patch-clamp experiments using cells expressing hERG showed that (S)-methadone blocked the hERG current 3.5-fold more potently than (R)-methadone (IC50s (half-maximal inhibitory concentrations) at 37 degrees C: 2 and 7 microM). As CYP2B6 slow metabolizer (SM) status results in a reduced ability to metabolize (S)-methadone, electrocardiograms, CYP2B6 genotypes, and (R)- and (S)-methadone plasma concentrations were obtained for 179 patients receiving (R,S)-methadone. The mean heart-rate-corrected QT (QTc) was higher in CYP2B6 SMs (*6/*6 genotype; 439+/-25 ms; n=11) than in extensive metabolizers (non *6/*6; 421+/-25 ms; n=168; P=0.017). CYP2B6 SM status was associated with an increased risk of prolonged QTc (odds ratio=4.5, 95% confidence interval=1.2-17.7; P=0.03). This study reports the first genetic factor implicated in methadone metabolism that may increase the risk of cardiac arrhythmias and sudden death. This risk could be reduced by the administration of (R)-methadone.
Keywords AdultAllelesAnalgesics, Opioid/blood/chemistry/pharmacologyAryl Hydrocarbon Hydroxylases/metabolismDNA, Complementary/biosynthesis/geneticsElectrocardiography/drug effectsEther-A-Go-Go Potassium Channels/drug effectsFemaleGenotypeHeart Rate/drug effectsHumansKineticsLong QT Syndrome/chemically induced/genetics/physiopathologyMaleMethadone/blood/chemistry/pharmacologyMiddle AgedOxidoreductases, N-Demethylating/metabolismPatch-Clamp TechniquesPotassium Channel BlockersReverse Transcriptase Polymerase Chain ReactionStereoisomerism
PMID: 17329992
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EAP, C B. et al. Stereoselective block of hERG channel by (S)-methadone and QT interval prolongation in CYP2B6 slow metabolizers. In: Clinical Pharmacology and Therapeutics, 2007, vol. 81, n° 5, p. 719-28. doi: 10.1038/sj.clpt.6100120 https://archive-ouverte.unige.ch/unige:14363

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Deposited on : 2011-02-07

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