Preparation and in vitro evaluation of salbutamol-loaded lipid microparticles for sustained release pulmonary therapy

The aim of this study was to prepare lipid microparticles (LMs) loaded with the polar bronchodilator agent salbutamol, and designed for sustained release pulmonary delivery. The microparticles were produced by melt emulsification followed by a sonication step, using different biocompatible lipid carriers (tristearin, stearic acid and glyceryl behenate) and phosphatidylcholine as the surfactant. The use of salbutamol free base, rather than salbutamol sulphate, was necessary to obtain the incorporation of the drug in the lipid particle matrix. The prolonged release of salbutamol base was achieved only by the glyceryl behenate microparticles (40.9% of encapsulated drug being released after 8 h). The salbutamol loading was 4.2% ± 0.1 and the mass median diameter, determined by laser diffraction, ranged from 4.8 to 5.4 µm. The sustained release of LMs were formulated as a carrier-free dry powder for inhalation and exhibited a fine particle fraction of 17.3% ± 2.2, as measured by multi-stage liquid impinger.