Effect of Agitation Intensity on the Dissolution Rate of Indomethacin and Indomethacin-Citric Acid Compressed Discs

The dissolution rates of indomethacin (IMC) and indomethacin-citric acid (monohydrate) 1:1 mixtures under various hydrodynamic conditions were determined in a phosphate buffered medium Dissolution profiles of the γ form of IMC were nonlinear the rates decreasing with time The dissolution rates increased with increasing stirring speed In contrast α-IMC gave linear dissolution profiles the rates being higher and more sensitive to agitation intensity than those obtained using the γ-form. The slope of a log dissolution rate versus log stirring speed plot had a value of 0.598 for γ-IMC and 0.171 for γ-IMC Indomethacin dissolution rates from the mixed discs were 5-10 times lower than those of pure γ-IMCin the stirring speed range 180-60 rpm respectively The dissolution profiles of IMC showed positive curvature at low stirring speed while at high stirring speed the dissolution profiles became linear The slope of the log dissolution rate versus log stirring speed plot was nonlinear and ranged from >1 at low stirring speed to <0.5 at high stirring speed.