Skip to main content
. Author manuscript; available in PMC: 2013 Jun 18.
Published in final edited form as: Clin Pharmacol Ther. 2011 Dec 14;91(2):227–233. doi: 10.1038/clpt.2011.217

Table 2. Parameter estimates for sigmoidal curve fits of tariquidar concentrationaversus effect measures in humans and rats.

Effect measure (human)b Emax EC50 (ng/mL) n R2
VT–VT baseline (2T4K)c 0.9±0.1 561±24 11.3±5.4 0.789
K1–K1 baseline (2T4K)c 0.061 ±0.008 526±41 6.3±3.5 0.668
K1–K1 baseline (1T2K)d 0.059±0.007 521±40 6.2±3.5 0.673
Effect measure (rat) e E max EC50 (ng/mL) n R2
VT–VT baselinec (2T4K)f 11.8±0.3 544±32 2.5±0.5 0.974
K1–K1 baselinec (2T4K)f 1.0±0.1 441±81 1.9±0.8 0.812
a

Tariquidar plasma concentrations at end of PET scan measured with liquid chromatography tandem mass spectrometry.

b

Baseline values in humans: VT (2T4K), 0.66±0.12; K1 (2T4K), 0.036±0.01; K1 (1T2K), 0.035±0.01.

c

Data from 0-40 min after radiotracer injection were used.

d

Data from 0-10 min after radiotracer injection were used.

e

Baseline values in rats: VT (2T4K), 1.27±0.15; K1 (2T4K), 0.16±0.05.

f

Data from 0-60 min after radiotracer injection were used.

Emax, maximum effect; EC50, half-maximum effect concentration of tariquidar in plasma (ng/mL); n, Hill coefficient; R2, coefficient of determination; VT, volume of distribution; K1, influx rate constant from plasma into first brain tissue compartment; 2T4K, 2-tissue-4-rate constant compartment model; 1T2K, 1-tissue-2-rate constant compartment model.