Losartan, the first of a new class of antihypertensives, is a specific and selective antagonist of angiotensin II at the AT1 sites. Angitensin II is a potent vasoconstrictor, the primary vasoactive hormone of the renin-angiotensin system and an important component in the pathophysiology of hypertension. Losartan and its principal active metabolite block the vasoconstriction and aldosterone secreting effects of angiotensin II to the AT1 receptor found in many tissues. Losartan is now regarded as the first-line therapy option for treating high blood pressue.
The usual starting and maintenance dose is 50 mg once daily for most patients. The maximal antihypertensive effect is attained 3-6 weeks after initiation of therapy. Some patients may receive an additional benefit by increasing the dose to 100 mg once daily. In patients who are salt depleted corrective measures should be used before starting Losartan and the initial dose should be reduced to 25 mg. Losartan may be administered with other antihypertensive agents. Losartan may be administered with or without food.
No initial dosage adjustment is necessary in patients with mild renal impairment (CrCl 20-50 ml/min). For patients with moderate to severe renal impairment (CrCl < 20 ml/min) or patients on dialysis, a lower starting dose of 25 mg is recommended. Use in elderly: Patients up to 75 years: No initial dosage adjustment is necessary for this group of patients. Patients over 75 years: A lower starting dose of 25 mg once daily is recommended.