Preparation and characterization of solid lipid microparticles containing propafenone hydrochloride.

Purpose: To produce microparticles containing highly concentrated drug (Propafenone hydrochloride, PRF) by means of a new pneumatic nozzle for spray congealing and to evaluate the effect of the spray process on the microparticle characteristics. Methods: Microparticles with a theoretical drug loading of 50% w/w were produced by the spray congealing process using a wide pneumatic nozzle (WPN). 6 batches with different formulation based on cetearyl alcohol and containing different thickening and suspending agents (AerosilÒ R812 and R972 and soya lecithin) were prepared. Results: Using the spray congealing technology by means of the WPN, it was possible to obtain PRF/cetearyl alcohol microparticles with a theoretical drug loading of 50% w/w (corresponding to 300 mg of microparticles with a PRF dose of 150 mg). For all formulations, the yield was higher than 90% and the EE was around 95-98%. PRF was uniformly distributed within the microparticles when Aerosil was added. The main particle size ranged from 75 to 250 mm. The results of viscosity measurements evidenced that increasing the viscosity of the fluid to be atomized, the amount of particle size lower than 250 mm decreased, while the amount of particle size larger than 250 mm increased. The microparticles appeared spherical with a rough surface and showed controlled release profiles for 8 h. DSC scans indicated the permanence of PRF in the original crystalline form (mp=176.8±0.54°C). Conclusions: the performance of the spray-congealing system by means of the WPN was excellent as the nozzle was able to produce stable SLM (after 12 month of storage) with high drug loading and good yields, upon the high viscosity of the melted mixture. The SLM showed a narrow Gaussian size distribution, a spherical shape and a controlled release profile.