Losartan is NOT a Diuretic
Losartan is an angiotensin II receptor antagonist (ARB), not a diuretic—it belongs to a completely different drug class with a distinct mechanism of action. 1, 2
Mechanism of Action
- Losartan selectively blocks the angiotensin II type 1 (AT1) receptor, preventing angiotensin II from binding and exerting its effects on blood pressure and fluid balance 2, 3
- This mechanism is fundamentally different from diuretics, which increase sodium and water excretion through the kidneys 1
- Losartan and its active metabolite E-3174 provide blood pressure reduction through vasodilation and reduced aldosterone secretion, not through diuresis 4
Clinical Classification
Major hypertension guidelines consistently classify losartan separately from diuretics:
- The 2007 European Society of Hypertension/Cardiology guidelines list five distinct drug classes for initiating hypertension treatment: thiazide diuretics, calcium antagonists, angiotensin receptor antagonists (including losartan), ACE inhibitors, and β-blockers 1
- These guidelines explicitly distinguish angiotensin receptor antagonists as a separate therapeutic category from diuretics 1
- Clinical trials comparing antihypertensive agents consistently categorize losartan as an ARB, not as a diuretic 1
Important Clinical Distinction
- Losartan is often combined WITH diuretics (particularly hydrochlorothiazide) to enhance blood pressure control, which demonstrates they are separate drug classes with complementary mechanisms 2, 5, 4
- The combination provides additive antihypertensive effects precisely because they work through different pathways 5
Unique Uricosuric Property
- Interestingly, losartan has modest uricosuric effects (increases uric acid excretion), which is actually opposite to the hyperuricemic effects of thiazide diuretics 1, 2
- This property makes losartan particularly useful in patients with gout who require antihypertensive therapy, especially when discontinuing diuretics 1
Clinical Bottom Line
Losartan is definitively an angiotensin II receptor blocker, not a diuretic. While both classes lower blood pressure, they do so through entirely different mechanisms and are recognized as distinct therapeutic categories in all major clinical guidelines 1, 3, 6.