Abstract
Studies were made on the interaction of α- or β-cyclodextrin with seven kinds of barbituric acid derivatives and two kinds of analogous compounds, and it was found by solubility analysis that complexes were formed between both kinds of cyclodextrins and all of the barbiturates (including the analogous compounds) tested. The slopes of the solubilization isotherms were generally larger for β-cyclodextrin-barbiturate system than for α-cyclodextrin-barbiturate system. Barbiturates having a bulky substituent showed especially small interaction with α-cyclodextrin. Solubility analysis, and composition analysis of crystalline complexes showed that 2 : 1 complexes were formed between α-cyclodextrin and the barbiturates, and 1 : 1 complexes between β-cyclodextrin and the barbiturates. A possible explanation for such a difference was given. Deposition of free thiopental from aqueous preparation of sodium thiopental by absorption of atmospheric carbon dioxide was retarded to a large extent in the presence of α-cyclodextrin.
