The drug acts by preventing the action of a hormone called angiotensin II in the human body. Angiotensin II generally acts on special receptors in the body, with two major results. Losartan blocks the receptors that angiotensin II acts on, and so prevents its actions. This leads to a decrease in the salt and water retention by the kidneys as well as relaxation of the peripheral blood vessels, which results in control of blood volume and blood pressure.