STUDIES OF CYCLODEXTRIN INCLUSION COMPLEXES 1- INCLUSION COMPLEXES BETWEEN -AND -CYCLODEXTRINS AND CHLORAMPHENICOL IN AQUEOUS SOLUTIONS

Document Type : Original Article

Authors

Department of Pharmaceutics, Faculty of Pharmacy, Assiut University, Assiut, Egypt

Abstract

Chloramphenicol was found to form inclusion complexes with a-and b-cyclodextrine (a-CyD and b-CyD) in aqueous solution. Phase solubility diagrams were obtained with b-CyD and found to be BS type curve. An apparent 1:1 complex formation constant (Kc` of 8077x104 M-1 was obtained for chloramphenicol in b-CyD.
For a-CyD the phase solubility diagrams indicate AL type curves. The complex stochiometric ratios were found to be 1:1 and 1:2 (guest: host). The apparent formation constants (Kc ) for chloramphenicol in a-CyD were found to be 3017x104 M-1 and 957x104 M-1, for 1:1 and 1:2 stochiometric ratios respectively.
It was found that the aqueous solubility of chloramphenicol is enhanced by a- and b-CyD inclusion complexation than by the non-ionic surfactant solutions used in a previous study. The higher values obtained for the complex formation constants indicate a particularly good fitness of the chloramphenicol molecule within the b-and a-CyD cavities .
Microcrystalline solid inclusion complex of chloramphenicol and b-CyD 1:1 was isolated and investigated by I.R., in comparison to a physical mixture 1:1 to characterize the interaction arising between chloramphenicol and b-CyD within the complex.
The effect of certain water soluble carriers, in 5% w/v concentration on chloramphenicol complexation in a-and b-CyD cavities was investigated. The aim of adding such additives is to reduce the concentration of the CyDs used in formulating chloramphenicol in solution. It was found that propylene glycol and P.E.G. 4000 assist chloramphenicol complexation in b-CyD, forming higher Kc values; 46221 x 104 M-1  and 39883 x 104 M-1  respectively, while glycerol deminishes chloramphenicol complexation in b-CyD.
In case of a-CyD, P.E.G 4000 and propylene glycol rise Kc and Kc` for chloramphenicol respectively and the reverse is true for glycerol.