Interactions of .ALPHA.- and .BETA.-cyclodextrin with several non-steroidal antiinflammatory drugs in aqueou solution.

The interactions of α-cyclodextrin (α-CD) and β-cyclodextrin (β-CD) with several non-steroidal antiinflammatory drugs were studied, observing the effects of α- and β-CD on the solubility and the stability of the drugs in aqueous solution in comparison with that of glucose. Moreover, the combined effects of urea and sodium chloride with β-CD on the solubility of drugs were discussed. The solubility of all kinds of drugs was found to increase with the addition of β-CD, while not with glucose. The increase of solubility with β-CD was considered due mainly to the formation of inclusion compounds. From the solubility data, the apparent stability constant K of the formation of inclusion compound were calculated, and moreover the functional groups included by β-CD were estimated for the respective drugs. The dissolution rate of drug increased with β-CD, while not with glucose, as was similar in tendency to the solubility data. β-CD accelerated the degradation of azapropazone in aqueous solution while retarded that of phenylbutazone, and glucose had no effect on the stability of drugs, showing that a formations of inclusion compound with β-CD may make some drugs stable and others labile. The addition of urea was considered to promote the inclusion of drug with β-CD, while sodium chloride gave the opposite effect, and an elevation of temperature gave the promoting effect.