Effects of 2-hydroxypropyl-beta-cyclodextrin on the aqueous solubility of drugs and transdermal delivery of 17 beta-estradiol.

The effect of 2-hydroxypropyl-beta-cyclodextrin (2-HPCD) on the aqueous solubility of 18 drugs possessing different physiochemical properties was investigated. The largest increase in aqueous solubility was obtained with very lipophilic drugs with low aqueous solubility and the enhancement was larger at low temperature than at high temperature. In many cases a linear relationship exists between the drug solubility and the 2-HPCD concentration. Ionization of a drug molecule enhanced the solubility effects of 2-HPCD, resulting in greater aqueous solubility than if either method was used by itself. 2-HPCD was found to be an effective transdermal permeability enhancer.