Thermodynamic Studies of Drug--Cyclodextrin Interactions in Water at 298.15 K: Promazine Hydrochloride/Chlorpromazine Hydrochloride + -Cyclodextrin + H2O Systems
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- 作者：Santosh S. Terdale ; Dilip H. Dagade ; Kesharsingh J. Patil
- 刊名：Journal of Physical Chemistry B
- 出版年：2007
- 出版时间：December 6, 2007
- 年：2007
- 卷：111
- 期：48
- 页码：13645 - 13652
- 全文大小：127K
- 年卷期：v.111,no.48(December 6, 2007)
- ISSN：1520-5207
文摘
Data on osmotic coefficients have been obtained for a binary aqueous solution of two drugs, namely, promazinehydrochloride (PZ) and chlorpromazine hydrochloride (CPZ) using a vapor pressure osmometer at 298.15 K.The observed critical micelle concentration (cmc) agrees excellently with the available literature data. Themeasurements are extended to aqueous ternary solutions containing fixed a concentration of -cyclodextrin(-CD) of 0.1 mol kg-1 and varied concentrations (~0.005-0.2 mol kg-1) of drugs at 298.15 K. It has beenfound that the cmc values increase by the addition of -CD. The mean molal activity coefficients of the ionsand the activity coefficient of -CD in binary as well as ternary solutions were obtained, which have beenfurther used to calculate the excess Gibbs free energies and transfer Gibbs free energies. The lowering of theactivity coefficients of ions and of -CD is attributed to the existence of host-guest (inclusion)-type complexequilibria. It is suggested that CPZ forms 2:1 and 1:1 complexed species with -CD, while PZ forms only1:1 complexed species. The salting constant (ks) values are determined at 298.15 K for promazine--CDand chlorpromazine--CD complexes, respectively, by following the method based on the application ofthe McMillan-Mayer theory of virial coefficients to transfer free energy data. It is noted that the presenceof chlorine in the drug molecule imparts better complexing capacity, the effect of which gets attenuated asa result of hydrophobic interaction. The results are discussed from the point of view of associative equilibriabefore the cmc and complexed equilibria for binary and ternary solutions, respectively.