Table 2. Equilibrium Constants Measured for Various Drugs with Soluble HSA by Using Ultrafast Affinity Extraction on HSA Microcolumns^a.

association equilibrium constant, Ka, or global affinity constant, nKa′ (M–1)
drug	estimate (eq 6)	estimate (eqs 5 and 6)	literature [ref]
warfarin	2.4 (±0.4) × 105	1.6 (±0.2) × 105	2.0–5.7 × 105 [18, 29, 30]
tolbutamide	1.1 (±0.4) × 105	0.9 (±0.2) × 105	1.1 (±0.1) × 105 [19]b
acetohexamide	1.8 (±0.5) × 105	1.3 (±0.1) × 105	1.7(±0.1) × 105 [20]b
verapamil	1.5 (±0.4) × 104	1.6 (±0.2) × 104	1.4 (±0.1) × 104 [21]c
gliclazide	8.0 (±0.6) × 104	6.9 (±1.0) × 104	7.9 (±0.1) × 104 [22]b
chlorpromazine	6.2 (±0.5) × 104	4.9 (±0.5) × 104	6.4 × 104 [23]

^aThese results were measured at pH 7.4 and at 37 °C. The values in parentheses represent a range of ±1 S.D., as determined by error propagation.

^bThe global affinity constants for these drugs were calculated from data in the given references.

^cThis value represents the average association equilibrium constant for R- and S-verapamil at their high affinity site on HSA.