Table 2.

Binding constants, K_1:1 (M⁻¹), for various substrates, progesterone, testosterone, hydrocortisone, digoxin and phenytoin, with β-cyclodextrin (β-CD) and a number of modified β-cyclodextrins (see footnotes for details) from Rajewski (1990).

	Binding Constants, K1:1 (M−1)
	Progesterone	Testosterone	Hydrocortisone	Digoxin	Phenytoin
β-Cyclodextrin	NDf	1.78 × 104	4.12 × 103	2.82 × 104	1.51 × 103
6-Mono Sulfonatea	1.99 × 102	6.36 × 101	ND	ND	ND
6-Heptakis Sulfonateb	2.03 × 102	7.34 × 101	ND	ND	3.56 × 101
HP-β-CDc	1.12 × 104	1.16 × 104	1.34 × 103	4.90 × 103	1.07 × 103
SPE1-β-CDd	1.66 × 104	1.87 × 104	3.89 × 103	2.74 × 104	1.03 × 103
SPE3.6-β-CDd	1.19 × 104	1.43 × 104	1.74 × 103	1.41 × 104	1.31 × 103
SPE7-β-CDd	7.68 × 103	9.63 × 103	9.98 × 102	5.29 × 103	8.24 × 102
SBE1-β-CDe	1.72 × 104	1.64 × 104	3.83 × 103	2.76 × 104	1.22 × 103
SBE4.7-β-CDe	1.57 × 104	1.82 × 104	2.69 × 103	1.71 × 103	1.26 × 103
SBE7-β-CDe	1.83 × 104	2.25 × 104	2.15 × 103	6.88 × 103	7.56 × 102

^aMono-(6-deoxy-sulfonic acid)- β-cyclodextrin, sodium salt.

^bHeptakis-(6-deoxy-sulfonic acid)- β-cyclodextrin, sodium salt.

^cHydroxypropyl-β-cyclodextrin, Molecusol^TM, Pharmatec, Inc.

^dSulfopropylether-β-cyclodextrins with the degree of substitution indicated by the subscript after the SPE.

^eSulfobutylether-β-cyclodextrins with the degree of substitution indicated by the subscript after the SBE.

^fNot determined.