Effects of atomoxetine on the QT interval in healthy CYP2D6 poor metabolizers.
OBJECTIVE
The effects of atomoxetine (20 and 60 mg twice daily), 400 mg moxifloxacin and placebo on QT(c) 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 (QT(c)M) on day 7 was the primary endpoint.


RESULTS
QT(c)M 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 QT(c) was observed. The moxifloxacin difference from placebo met the a priori definition of non-inferiority. Maximum mean placebo-subtracted change from baseline QT(c)M 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-QT(c) change observed was consistent with the literature.


CONCLUSIONS
Atomoxetine was not associated with a clinically significant change in QT(c). However, a statistically significant increase in QT(c) was associated with increasing plasma concentrations.
Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA. loghincn@lilly.com
Corina
C
Loghin
Harry
H
Haber
Charles M
CM
Beasley
Prajakti A
PA
Kothare
Lynnette
L
Kauffman
John
J
April
Ling
L
Jin
Albert J
AJ
Allen
Malcolm I
MI
Mitchell
D018759:Adrenergic Uptake Inhibitors / Q000493:pharmacokinetics / Q000494:pharmacology*; D000328:Adult; D000069445:Atomoxetine Hydrochloride; D001372:Aza Compounds / Q000493:pharmacokinetics / Q000494:pharmacology*; D018592:Cross-Over Studies; D019389:Cytochrome P-450 CYP2D6 / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004562:Electrocardiography / Q000187:drug effects*; D024841:Fluoroquinolones; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D008297:Male; D000077266:Moxifloxacin; D011437:Propylamines / Q000493:pharmacokinetics / Q000494:pharmacology*; D011804:Quinolines / Q000493:pharmacokinetics / Q000494:pharmacology*; D059005:Topoisomerase II Inhibitors / Q000493:pharmacokinetics / Q000494:pharmacology*; D055815:Young Adult
D018759:Adrenergic Uptake Inhibitors; D001372:Aza Compounds; D024841:Fluoroquinolones; D011437:Propylamines; D011804:Quinolines; D059005:Topoisomerase II Inhibitors; D000069445:Atomoxetine Hydrochloride; D019389:Cytochrome P-450 CYP2D6; D000077266:Moxifloxacin