Fexofenadine is widely used drug for allergic conditions especially Rhiniti and is a selective histamine H1 receptor antagonist. In our recent research we study the effect of acidic and alkaline medium on four different brands of Fexofenadine, for this the solutions of different brands of Fexofenadine were subjected to neutral,alkaline and acidic medium. When Fexofenadine brands subjected to 0.1 N HCl and 0.1N NaOH for 30 minutes, Fexofenadine brands showed variable availability results. Xanidine and Telefast donot show any change in absorbance in acidic medium but shows a decrease in absorbance in alkaline medium. While Allerga shows a decrease in absorbance in both acidic and alkaline medium. Fexet also shows a decrease in absorbance in acidic medium but shows a increase in absorbance in alkaline medium.