Hot air coating microparticles: I. Drug release mechanism.

The aim of this work was to evaluate the kinetics and the mechanism of the drug release process from microparticles prepared by Hot Air Coating (HAC) technique. An antiarrhythmic drug (PRF06) was the active molecule and cetearyl alcohol and Pluronic F68 were the excipients. Setting the optimal operating conditions, microparticles were obtained; they were collected, separated by sieving into five size fractions and characterized. Drug release test was carried out on each single fraction of microparticles and the Weibull Function and the exponential kinetic model were applied to the experimental data. The results show that the size of the microparticles affects the drug release profile. Moreover the absence of a burst-effect indicates that the drug crystals are not on the particles surface, but are coated by the mixture of the excipients. The application of the Weibull model gives values of the Weibull parameter b close to 1, indicating that the shape of the dissolution curves is exponential. All the results suggest that a diffusive mechanism governs the drug release from HAC microparticles.