About Losartan Potassium An angiotensin II receptor antagonist, Antihypertensive. Mechanism of Action of Losartan Potassium It is a competitive antagonist of angiotensin-2 at AT-1 receptor. It decreases peripheral resistance and lowers BP in hypertensive individuals. It blocks all overt actions of angiotensin-2 such as: - 1. Vasoconstriction, 2. Central & Peripheral sympathetic stimulus, 3. Release of aldosterone and adrenaline, 4. Salt and water reabsorption, 5. Central actions like thirst, vasopressin release, and growth promoting actions on heart and blood vessels. Interactions for Losartan Potassium Diuretics, other antihypertensives: Potentiate the hypotensive effect of losartan. Potassium sparing diuretics, potassium suppliments: Risk of hyperkalaemia. NSAIDs: May blunt hypotensive effect of losartan. Cytochrome P450 inhibitors like ketoconazole: Increase in AUC of losartan by 18 % but has no effect on its active metabolite.