USE OF A POLAROGRAPHIC METHOD, A UV METHOD AND THE PHASE-SOLUBILITY TECHNIQUE TO DETERMINE THE STABILITY CONSTANT IN AQUEOUS-SOLUTION OF A BETA-CYCLODEXTRIN COMPLEX WITH A NEW IMMUNOMODULATING AGENT

A study was carried out using polarographic changes, UV spectroscopic changes, and the phase-solubility technique to investigate the stability constant in aqueous solution of the complex of beta-cyclodextrin (beta-CD) and FCE 24578 (2-cyano-3-(1,4-dihydro-1-phenyl-(1)-benzothiopyran-(4,3-C)-pyrazol-3-yl)-3-oxo-N-phenyl-propanamide), a new immunomodulating agent. We found values for the stability constant of the drug/beta-CD complex of 0.69-10(3) M-1 (obtained using the phase-solubility technique), 3.07-10(3) M-1 (obtained by U.V.) and of 1.04-10(3) M-1 (obtained by polarography). The polarographic method seems to be valuable for the determination of the stability constant of drug/beta-CD in solution. A very low amount of beta-CD is added to the solution when carrying out the measurement, to shift the equilibrium.