Investigation on the Key Factors of Affecting in Vitro Release of Losartan Potassium and Hydrochlorothiazide Tablets

OBJECTIVE To investigate the key factors of affecting in-vitro release of losartan potassium and hydrochlorothiazide tablets.METHODS The in vitro dissolution of the products were determined by paddle+sinker (the stirring speed was 50 r·min^-1) in pH 3.5 buffer solution as dissolution medium.The HPLC method was adopted using Kromasil 100-10 C₈,with mobile phase of 0.01 mol·L^-1monobasic potassium phosphate solution (pH 2.5)-acetonitrile (2:3),detection wavelength of 230 nm,injection volume of 20 μL,and flow rate of 2.3 mL·min^-1.RESULTS It was found that the coloring agent in the coating powder for the tablets was the main reason for the difference in dissolution between the self-prepared formulation and reference listing drug.Through further investigation,it was found that the morphology and properties of aluminum lakes could delay drug release in acid medium.In addition,the interaction between aqueous polymer hydroxypropyl-cellulose and pH 3.5 buffer solution was also an important factor toward delaying the drug release.CONCLUSION The types of coloring agent and aqueous polymer in immediate-release coating powder actually can directly affect drug product release.