What class of medication does losartan belong to?

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Losartan Drug Classification

Losartan is an angiotensin II receptor blocker (ARB), specifically a selective angiotensin II type 1 (AT1) receptor antagonist. 1

Mechanism of Action

  • Losartan selectively and completely blocks the binding of angiotensin II at the angiotensin type 1 (AT1) receptor, which represents a unique mechanism of action different from all other classes of antihypertensive agents 2
  • This provides a more specific and complete blockade of the actions of angiotensin II than renin or ACE inhibitors 3
  • The AT1 receptor blockade inhibits all well-known effects of angiotensin II, including vasoconstriction, aldosterone release, renin release (negative feedback), and stimulation of thirst 4

Chemical Structure and Pharmacology

  • Losartan potassium is a non-peptide molecule, chemically described as 2-butyl-4-chloro-1-[p-(o-1H-tetrazol-5-yl-phenyl)benzyl]-imidazole-5-methanol monopotassium salt with molecular formula C22H22ClKN6O 1
  • Losartan is the prototype and first of this new class of AT1-selective receptor antagonists to reach clinical use 5, 6
  • The parent compound has moderate affinity for the AT1 receptor (competitive inhibition) and is rapidly converted via oxidation in the liver to a more potent metabolite (E3174) with 20- to 30-times greater affinity for the AT1 receptor (non-competitive inhibition) 5

Clinical Context

  • Guidelines classify losartan within the ARB drug class alongside other agents such as valsartan, candesartan, and irbesartan for treatment of hypertension, heart failure, and diabetic nephropathy 7
  • The JNC 7 guidelines specifically identify losartan as an ARB when comparing it to other antihypertensive drug classes including ACE inhibitors, beta-blockers, calcium channel blockers, and diuretics 7

References

7
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

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This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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