Drug Class of Losartan
Losartan belongs to the angiotensin II receptor blocker (ARB) class of medications, specifically acting as a selective antagonist of the AT1 receptor subtype.
Mechanism of Action
Losartan works by:
- Competitively and selectively binding to the angiotensin II subtype 1 (AT1) receptor 1
- Blocking angiotensin II-induced physiological effects 2
- Converting to an active metabolite (E3174) that is 10-40 times more potent than losartan itself 3
- Providing a non-peptide alternative to ACE inhibitors for blocking the renin-angiotensin system 4
Classification Details
ARBs like losartan are distinguished from other antihypertensive medications:
- Unlike ACE inhibitors which prevent the formation of angiotensin II, ARBs block the binding of angiotensin II to its receptor 5
- ARBs are sometimes referred to as "sartans" based on their common suffix
- The FDA label officially classifies losartan as an "angiotensin receptor blocker (ARB)" 4
- The European Society of Cardiology and European Society of Hypertension guidelines refer to this class as "angiotensin receptor antagonists" 6
Clinical Context
ARBs like losartan are commonly used in:
- Hypertension management
- Heart failure treatment
- Diabetic nephropathy
- Prevention of stroke in patients with left ventricular hypertrophy 4
Comparison to Related Drug Classes
ARBs differ from ACE inhibitors in several important ways:
- ARBs cause significantly less cough than ACE inhibitors (only 17-29% of patients who experienced ACE inhibitor-induced cough develop cough on losartan) 7
- Both classes block the renin-angiotensin system but through different mechanisms
- ARBs may be preferred in patients who cannot tolerate ACE inhibitors due to cough or angioedema 5
Important Considerations
- Losartan is contraindicated in pregnancy (Category D) and should be discontinued immediately if pregnancy is detected 7, 4
- Dual RAS blockade (combining ARBs with ACE inhibitors) should be avoided as it increases adverse effects without significant clinical benefit 7
- Potassium supplements, salt substitutes containing potassium, diuretics, lithium, and NSAIDs may interact with losartan 4
ARBs like losartan represent an important class of cardiovascular medications with proven benefits in blood pressure control and organ protection, particularly for patients who cannot tolerate ACE inhibitors.