Formulation, optimization, and in vitro/in vivo evaluation of furosemide nanosuspension for enhancement of its oral bioavailability

Furosemide is a poorly soluble diuretic used for treatment of hypertension and edema. It has very poor or variable oral bioavailability due to its reduced solubility in gastric fluid and reduced permeability in intestinal fluid. The aim of this study was to prepare nanosuspension of furosemide to enhance its oral bioavailability by increasing its dissolution in stomach where it has better permeability. Full factorial design was used for a systematic approach of formulation and optimization. The nanosuspensions were prepared by precipitation with ultrasonication method. Polyvinyl acetate was used for sterically stabilizing the nanosuspensions. The diffusing drug concentration and stabilizer were used as the factors and the particle size, polydispersity index, and drug release were selected as dependent variables and characterized. The effect of nanoprecipitation on enhancement of oral bioavailability of furosemide nanosuspension was studied by in vitro dissolution and in vivo absorption studies in rats and compared to pure drug. Quality by design using full factorial design provided a systematic approach in optimizing nanosuspensions to produce products with desired quality. Stable nanosuspension were obtained with average size range of the precipitated nanoparticles between 150 and 300 nm and were found to be homogenous showing a narrow polydispersity index of 0.3 ± 0.1. The in vivo studies on rats revealed a significant increase in the oral absorbtion of furosemide in the nanosuspension compared to pure drug. The AUC0→24 and Cmax values of nanosuspension were approximately 1.38- and 1.68-fold greater than that of pure drug, respectively. Furosemide nanosuspension showed 20.06 ± 0.02 % decrease in systolic blood pressure compared to 13.37 + 0.02 % in plain furosemide suspension, respectively. The improved oral bioavailability and pharmacodynamic effect of furosemide may be due to the improved dissolution of furosemide in simulated gastric fluid which results in enhanced oral systemic absorption of furosemide from stomach region where it has better permeability.