Losartan Drug Classification
Losartan is an angiotensin II receptor blocker (ARB), also known as an angiotensin II type 1 receptor antagonist, which selectively blocks the AT1 receptor to prevent the vasoconstrictor and aldosterone-secreting effects of angiotensin II. 1
Pharmacological Class
- Losartan belongs to the angiotensin II receptor antagonist (ARB) class of medications, specifically acting as a competitive antagonist at the AT1 receptor subtype 2, 1
- It is classified as a nonpeptide angiotensin II receptor antagonist, distinguishing it from earlier peptide-based compounds 1, 3
- Losartan was the first orally active angiotensin II receptor antagonist to be marketed and reach clinical use 4, 3, 5
Mechanism of Action
- Losartan and its active metabolite selectively block the binding of angiotensin II to the AT1 receptor found in vascular smooth muscle, adrenal gland, and other tissues 1
- The drug exhibits approximately 1000-fold greater affinity for the AT1 receptor than for the AT2 receptor, providing selective AT1 blockade 1
- Losartan acts as a reversible, competitive inhibitor of the AT1 receptor, while its active metabolite (E-3174) functions as a noncompetitive antagonist that is 10 to 40 times more potent than the parent compound 1, 6
- Unlike ACE inhibitors, losartan does not inhibit ACE (kininase II) and does not affect bradykinin metabolism 1, 5
Clinical Context
- ARBs like losartan are used for treatment of hypertension, heart failure with reduced ejection fraction, and diabetic nephropathy 2
- In clinical guidelines, ARBs are considered appropriate therapy for patients with cardiovascular disease who are intolerant of ACE inhibitors, particularly due to cough 2
- The American Heart Association and European Society of Cardiology classify losartan within the broader category of renin-angiotensin system (RAS) inhibitors, alongside ACE inhibitors 2