Interaction of several nonsteroidal antiinflammatory drugs with pectin in aqueous solution and in solid state.

Abstract

Interaction between several nonsteroidal antiinflammatory drugs and pectin was studied by the centrifugation method, the equilibrium dialysis method and the solubility method. Benzydamine hydrochloride (BZM) and ketoprofen (KPF) formed coprecipitates with pectin by the centrifugation method, and the binding isotherms of BZM and pectin showed a multi-layer type. On the other hand, the binding isotherm of BZM to pectin by the equilibrium dialysis method showed a Langmuir type in low equilibrium concentration range and the saturated amount bound decreased with an increase of ion concentration of the solution. The solubility of all drugs used decreased with an increase of concentration of pectin. IR absorption spectroscopy, X-ray diffraction pattern and differential scanning calorimetry of the BZN/pectin coprecipitate showed clear difference from the physical mixture. The dissolution rate of BZM/pectin coprecipitate and physical mixture of BZM and pectin was very slow in comparison with intact BZM and physical mixture of BZM and galacturonic acid. Pectin forms water insoluble complexes with these nonsteroidal antiinflammatory drugs, suggesting a usefulness as an additive for sustained-release preparations, and this might afford a mean for reducing adverse reactions of nonsteroidal antiinflammatory drugs to stomach after oral administration.