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. Author manuscript; available in PMC: 2013 Dec 9.
Published in final edited form as: J Clin Pharmacol. 2011 Nov 1;52(9):10.1177/0091270011416939. doi: 10.1177/0091270011416939

Table III.

Pharmacodynamic Modeling Parameters for Effect of Ibutilide on QT Intervals in Patients With Heart Failure and in Patients With Normal Left Ventricular Function

Parameter Heart Failure (n = 6) Normal Left Ventricular
Function (n = 9) 		P
EC50, μg/L 0.48 (0.46-0.49) 1.85 (1.10-3.23) .008
Emax, s 0.491 (0.475-0.519) 0.545 (0.517-0.576) .07
Hill coefficient (λ) 3.21 (1.52-7.16) 0.75 (0.58-3.67) .22
Keo, h−1 0.20 (0.10-7.20) 0.04 (0.02-0.07) .05

Data presented as median (interquartile range). EC50, serum ibutilide concentration at which 50% of the maximum QTF interval effect occurs. Emax, maximum model–derived effect on QTF interval. Keo, equilibrium rate constant from the central compartment to the theoretical effect compartment.