Overview
Losartan is an angiotensin II receptor blocker (ARB) used primarily for the treatment of hypertension. It works by selectively blocking the binding of angiotensin II to the AT1 receptor, leading to vasodilation and reduced blood pressure. It is also indicated for diabetic nephropathy in patients with type 2 diabetes and hypertension, and to reduce stroke risk in patients with hypertension and left ventricular hypertrophy.
Mechanism of Action
Losartan selectively blocks the angiotensin II type 1 (AT1) receptor, inhibiting the vasoconstrictive and aldosterone-secreting effects of angiotensin II. This results in vasodilation, reduced peripheral resistance, and decreased blood pressure without affecting bradykinin metabolism.
Indications
- Treatment of hypertension
- Reduction of stroke risk in patients with hypertension and left ventricular hypertrophy
- Treatment of diabetic nephropathy with an elevated serum creatinine and proteinuria in patients with type 2 diabetes and hypertension
Common Doses
- 25 mg
- 50 mg
- 100 mg
Dosage
Hypertension: Initial dose 50 mg once daily, may be increased to 100 mg once daily. Hypertensive patients with left ventricular hypertrophy: Start 50 mg once daily, add hydrochlorothiazide 12.5 mg daily and/or increase losartan to 100 mg daily. Nephropathy in type 2 diabetes: 50 mg once daily, may be increased to 100 mg once daily based on blood pressure response.
Contraindications
- Hypersensitivity to any component of losartan products
- Coadministration with aliskiren in patients with diabetes
Side Effects
- Dizziness
- Upper respiratory infection
- Fatigue
- Hypotension
- Hyperkalemia
- Increased serum creatinine
- Back pain
- Diarrhea
- Cough (less frequent than with ACE inhibitors)
Interactions
- Potassium supplements or potassium-sparing diuretics (risk of hyperkalemia)
- NSAIDs (may reduce antihypertensive effect and worsen renal function)
- Lithium (increased lithium levels)
- Aliskiren (contraindicated in patients with diabetes)
Counseling Points
- Take once daily with or without food
- Report dizziness, lightheadedness, or fainting, especially when standing up
- Avoid potassium supplements or salt substitutes containing potassium unless prescribed
- Notify healthcare provider if pregnancy is suspected or planned
- Regular blood pressure monitoring is essential
- Do not stop medication abruptly without medical advice