Is Losartan a Diuretic?
No, losartan is not a diuretic—it is an angiotensin II receptor antagonist (ARB) that blocks the AT1 receptor to lower blood pressure through a completely different mechanism than diuretics. 1
Mechanism of Action
- Losartan works by selectively and competitively blocking angiotensin II at the AT1 receptor, preventing vasoconstriction and aldosterone release 2, 3
- This mechanism is fundamentally different from diuretics, which promote sodium and water excretion through the kidneys 1
- The parent compound losartan is converted to an active metabolite (E-3174) that provides most of the antihypertensive effect over 24 hours 4, 5
Why the Confusion May Arise
- Losartan is frequently combined with hydrochlorothiazide (a thiazide diuretic) in fixed-dose combination products for enhanced blood pressure control 1, 6
- In heart failure trials, losartan was studied in addition to loop diuretics and other medications, not as a replacement for them 1
- Losartan has a modest uricosuric effect (increases uric acid excretion), which is sometimes confused with diuretic action, but this does not make it a diuretic 1, 4
Clinical Context
- Guidelines classify losartan as an alternative to ACE inhibitors for patients who cannot tolerate them (particularly those with ACE inhibitor-induced cough) 1
- In heart failure management, ARBs like losartan are used alongside diuretics, not instead of them—patients typically receive both a diuretic (for volume management) and an ARB (for neurohormonal blockade) 1
- The 2012 ESC guidelines explicitly state that ARBs reduce heart failure hospitalizations when added to conventional therapy that includes a diuretic 1
Common Pitfall to Avoid
Do not discontinue or avoid prescribing diuretics when starting losartan in patients who need volume management. Losartan provides neurohormonal blockade through the renin-angiotensin system but does not replace the volume-reducing effects of true diuretics 1.