Improved pH-independent dissolution and oral absorption of valsartan via the preparation of solid dispersion

Abstract

This study aimed to improve the pH-independent solubility and dissolution characteristics of valsartan via the preparation of solid dispersions (SD) with poloxamer 407. SDs was prepared by using the solvent method at various drug-polymer ratios and their dissolution characteristics were examined at different pHs. Oral pharmacokinetics of SDs was also evaluated in rats. Compared to the untreated powder, SDs significantly improved the dissolution rate as well as the extent of drug release at low pH. Particularly, SD having the drug-polymer ratio of 1:5 exhibited pH-independent dissolution of valsartan, resulting in the rapid and complete drug release over the pH range of 1.2 to 6.8. The improved dissolution of valsartan via SD formulation appeared to be well correlated with the enhanced oral exposure of valsartan in rats. SDs increased C(max) and AUC(0-24) of valsartan by 2-7 folds in rats, implying that SDs should be effective to improve the bioavailability of valsartan. In conclusion, SDs containing poloxamer 407 appeared to be effective to improve the pH-independent dissolution and oral absorption of valsartan.