Enhancement of the dissolution and diuretic effect of furosemide through a novel complexation with humic acid extracted from shilajit

Furosemide, a thiazide diuretic exhibits extremely low aqueous solubility. This study investigated the effects of complexation of furosaemide with humic acid extracted from shilajit on release rate and in vivo diuretic effect on male Wistar rats. Solid complexes of furosemide with humic acid extracted from shilajit were prepared by solvent evaporation and freeze drying methods in the molar ratio 1:1 and 1:2 (furosemide: humic acid). The complexes were characterized by differential scanning calorimetry, fourier transform infrared spectroscopy and scanning electron microscopy. The comparative release study of furosemide and complexes were carried out in phosphate buffer of pH 5.8. Solvent evaporated and freeze dried complex showed significant improvement in release rate as compared to pure furosemide. Maximum release was observed by the freeze dried complex in the molar ratio 1:2. The optimized complex (1:2 freeze dried) showed significant increase in diuresis in male Wistar rats as compared to pure furosemide. This study confirms that humic acid have a potential to increase the bioavailability of low bioavailable drugs.