INVESTIGATION OF THE INFLUENCE OF COSOLVENTS AND SURFACTANTS ON THE COMPLEXATION OF DEXAMETHASONE WITH HYDROXYPROPYL-BETA-CYCLODEXTRIN BY USE OF A SIMPLEX LATTICE DESIGN

Aqueous solutions of hydroxypropyl-beta-cyclodextrin were mixed with d ifferent amounts of propylene glycol, ethanol, Cremophor RH 40(R), and Solutol HS 15(R). The ternary blends were checked for their ability t o solubilize the lipophilic drug dexamethasone. To reduce the number o f experiments a simplex lattice design was applied. The fitted models were used to predict the solubilization behaviour of the different ble nds. The strongest antagonistic effect could be detected adding propyl ene glycol to aqueous hydroxypropyl-beta-cyclodextrin solutions. Small er but still antagonistic effects were found for the surfactants Cremo phor RH 40(R) and Solutol HS 15(R). Compared with pure aqueous hydroxy propyl-beta-cyclodextrin solutions, neither antagonistic nor synergist ic effects could be measured after addition of ethanol.