Effects of atomoxetine on the QT interval in healthy CYP2D6 poor metabolizers

• Published in: British journal of clinical pharmacology Vol. 75; no. 2; pp. 549 - 564
• Main Authors: Loghin, Corina, Haber, Harry, Beasley, Charles M., Kothare, Prajakti A., Kauffman, Lynnette, April, John, Jin, Ling, Allen, Albert J., Mitchell, Malcolm I.
• Format: Journal Article
• Language: English
• Published: England Blackwell Science Inc 01.02.2013
• Subjects: Adrenergic Uptake Inhibitors - pharmacokinetics; Adrenergic Uptake Inhibitors - pharmacology; Adult; atomoxetine; Atomoxetine Hydrochloride; Aza Compounds - pharmacokinetics; Aza Compounds - pharmacology; Cross-Over Studies; Cytochrome P-450 CYP2D6 - metabolism; Dose-Response Relationship, Drug; Drug Safety; Electrocardiography - drug effects; Fluoroquinolones; Heart Rate - drug effects; Humans; ICH E14; Male; moxifloxacin; Propylamines - pharmacokinetics; Propylamines - pharmacology; QTc; Quinolines - pharmacokinetics; Quinolines - pharmacology; thorough QT; Topoisomerase II Inhibitors - pharmacokinetics; Topoisomerase II Inhibitors - pharmacology; Young Adult
• ISSN: 0306-5251; 1365-2125
• DOI: 10.1111/j.1365-2125.2012.04382.x

Aim The effects of atomoxetine (20 and 60 mg twice daily), 400 mg moxifloxacin and placebo on QTc in 131 healthy CYP2D6 poor metabolizer males were compared. Methods Atomoxetine doses were selected to result in plasma concentrations that approximated expected plasma concentrations at both the maximum recommended dose and at a supratherapeutic dose in CYP2D6 extensive metabolizers. Ten second electrocardiograms were obtained for time‐matched baseline on days −2 and −1, three time points after dosing on day 1 for moxifloxacin and five time points on day 7 for atomoxetine and placebo. Maximum mean placebo‐subtracted change from baseline model‐corrected QT (QTcM) on day 7 was the primary endpoint. Results QTcM differences for atomoxetine 20 and 60 mg twice daily were 0.5 ms (upper bound of the one‐sided 95% confidence interval 2.2 ms) and 4.2 ms (upper bound of the one‐sided 95% confidence interval 6.0 ms), respectively. As plasma concentration of atomoxetine increased, a statistically significant increase in QTc was observed. The moxifloxacin difference from placebo met the a priori definition of non‐inferiority. Maximum mean placebo‐subtracted change from baseline QTcM for moxifloxacin was 4.8 ms and this difference was statistically significant. Moxifloxacin plasma concentrations were below the concentrations expected from the literature. However, the slope of the plasma concentration−QTc change observed was consistent with the literature. Conclusion Atomoxetine was not associated with a clinically significant change in QTc. However, a statistically significant increase in QTc was associated with increasing plasma concentrations.