Losartan is an oral prescription medicine in the angiotensin II receptor blocker (ARB) class. It is used to treat hypertension, reduce the risk of stroke in selected patients, and treat kidney disease associated with type 2 diabetes. It lowers blood pressure by blocking the effects of angiotensin II rather than by directly inhibiting its production. (medlineplus.gov)
Mechanism of action
Angiotensin II is a component of the renin–angiotensin–aldosterone system, which regulates blood pressure and fluid balance. It constricts blood vessels and stimulates the adrenal cortex to release aldosterone. Losartan and its principal active metabolite selectively block angiotensin II at the type 1 receptor, designated , thereby reducing these effects. The active metabolite is more potent by weight than losartan itself. (fda.gov)
Neither losartan nor its active metabolite inhibits angiotensin-converting enzyme (ACE). Its mechanism therefore differs from that of ACE inhibitors, although both drug classes act on the same hormonal system. (fda.gov)
Clinical uses
Losartan may be used alone or with other blood-pressure-lowering medicines. It controls hypertension but does not cure the underlying condition; its full blood-pressure-lowering effect may take several weeks to develop. (medlineplus.gov)
Its principal United States indications include:
- Hypertension: treatment in adults and children aged six years and older.
- Stroke-risk reduction: treatment of patients with hypertension and left ventricular hypertrophy, a thickening of the muscular wall of the heart’s main pumping chamber. The United States label states that evidence does not support the same stroke-risk benefit in Black patients.
- Diabetic nephropathy: treatment of patients with type 2 diabetes, a history of hypertension, elevated serum creatinine, and substantial urinary protein loss. In this population, losartan reduces progression to specified kidney outcomes. (dailymed.nlm.nih.gov)
Losartan is also sometimes used for heart failure, although this is not among the indications listed in the United States Cozaar label. (medlineplus.gov)
Evidence for kidney protection
The RENAAL randomized controlled trial, published in 2001, studied 1,513 patients with type 2 diabetes and nephropathy. Losartan or placebo was added to conventional antihypertensive treatment. Over a mean follow-up of 3.4 years, losartan reduced the relative risk of the combined outcome of doubling serum creatinine, end-stage kidney disease, or death by 16%. It reduced the kidney components of this outcome but did not reduce overall mortality. These findings concern the trial’s defined patient population rather than every form of chronic kidney disease. (pubmed.ncbi.nlm.nih.gov)
Safety and interactions
Recognized adverse effects include dizziness and symptomatic low blood pressure. Important risks include increased blood potassium and deterioration of kidney function, particularly in susceptible patients. Hypersensitivity reactions, including swelling affecting the face or airway, can occur. (dailymed.nlm.nih.gov)
Losartan carries a United States boxed warning for fetal toxicity. Exposure during pregnancy can cause fetal injury or death, especially through disruption of fetal kidney function. (dailymed.nlm.nih.gov)
Important interactions include potassium-raising medicines or supplements, lithium, and nonsteroidal anti-inflammatory drugs. Combining losartan with other medicines that inhibit the renin–angiotensin system increases risks of hypotension, kidney impairment, and high potassium. Concomitant use with aliskiren is contraindicated in patients with diabetes. (dailymed.nlm.nih.gov)
Formulations and regulatory history
Medicinal losartan is supplied as losartan potassium. Cozaar tablets contain 25, 50, or 100 mg of this salt. Losartan is also available in combination products containing hydrochlorothiazide, including Hyzaar. (fda.gov)
The United States Food and Drug Administration approved Cozaar on April 14, 1995. (fda.gov)
References
- DailyMed — COZAAR, losartan potassium tablet, film coateddailymed.nlm.nih.gov
- Losartan: MedlinePlus Drug Informationmedlineplus.gov
- FDA Clinical Pharmacology Review: Losartan Potassium Oral Suspensionfda.gov
- Effects of losartan on renal and cardiovascular outcomes in patients with type 2 diabetes and nephropathypubmed.ncbi.nlm.nih.gov
- FDA Cross-Discipline Team Leader Reviewfda.gov