Modeling of Association Properties of Cetylpyridinium Halides (Cl, Br) and their Influence on Liberation and Rheological and pH Balances of Hydrogels with Ibuprofen

Abstract

Abstract The paper studies the influences of two cationic surfactants - cetylpyridinium chloride (CPCl) and cetylpyridinium bromide (CPBr) - at concentrations 10-times below and 10-times above the CMC - at 258C-408C on the release of ibuprofen from hydrogels, rheological properties and pH. The association of surfactants in the water solutions was studied by conductometry. It was found that the temperature dependences of the surfactants’ CMCs are not linear and the CMCs of CPCl are higher than that of CPBr. The concentrations of the polymer (chitosan) and the drug were kept constant. Amounts of the released drug increased with the increasing temperature. From the hydrogels with CPBr and CPCl, whose surfactant concentration was below the respective CMC, higher amounts of the active ingredient were released than from the hydrogels with surfactant concentrations above the respective CMC. It is shown that for increasing temperature the hydrogels exhibit gradual transition for pseudo plastic to thixotropic system, what is advantageous for their practical application. The hydrogels’ pH values were in the interval 5.10-5.46, which is ideal for their application on the skin and for the chitosan swelling. The presented topic is a precondition of synthesis of the on-line and off-line control algorithms of an optimal release kinetics, elaborated by the authors.