Dry powder inhalation for sildenafil citrate: formulation and performance tests

Pulmonary arterial hypertension (PAH) is a severe disease responsible for high mortality in the affected population. Due to the limitations in treatment as severe adverse effects, high cost, we aimed to develop a simple therapeutic option for pulmonary administration, using a vasodilator sildenafil citrate (SILC) in a dry powder inhalation using lactose as carrier. A formulation of micronized SILC was prepared after 30 min wet grinding of the active with the aid of a vibration shear-mill. Solid characterization by laser diffraction and X-ray powder diffraction was assessed for active. Performance tests such as delivered-dose uniformity (DDU) and aerodynamic particle size distribution (APSD), using Dosage Unit Sampling Apparatus and Andersen Cascate Impactor, respectively, were performed. The micronization of SILC resulted in a medium size of 4.54 μm and a 50th percentile of 2.93 μm. For DDU, the total amount delivered ranged from 92.42 to 109.05% of the targeted dose, in agreement with the specified range (75.0-125.0%). For ASPD, a fine particle fraction of 35% was satisfactorily obtained. This formulation is simple and promising therapeutic option for the treatment of PAH with the advantage of being easily produced using less complex carrier matrix or equipment, in a short time.