Angiotensin II Receptor Blockers (ARBs) are cornerstone drugs in modern cardiovascular and renal medicine. They are especially important in hypertension, heart failure, and diabetic kidney disease, and are frequently tested as the preferred alternative to ACE inhibitors.
What Are ARBs?
ARBs selectively block the Angiotensin II type-1 (AT₁) receptor, preventing angiotensin II from exerting its harmful effects.
Why This Matters
Angiotensin II causes:
- Vasoconstriction
- Aldosterone release
- Sodium & water retention
- Cardiac and renal remodeling
Blocking its receptor leads to BP reduction and organ protection.
%20-%20Losartan,%20Valsartan,%20Candesartan%20and%20Irbesartan.jpg "Angiotensin II Receptor Blockers (ARBs) - Losartan, Valsartan, Candesartan and Irbesartan")
RAAS Recap (Quick Review)
| Step | Normal Action |
|---|---|
| Renin | Angiotensinogen → Angiotensin I |
| ACE | Angiotensin I → Angiotensin II |
| Angiotensin II | Vasoconstriction + Aldosterone |
| Aldosterone | Na⁺ & water retention |
ARBs block angiotensin II at the receptor level.
Mechanism of Action (Very High-Yield)
Step-by-Step
1. ARBs block AT₁ receptorsKey Difference from ACE Inhibitors
- No increase in bradykinin
- Therefore no dry cough
One-Line Exam Answer
ARBs lower blood pressure by blocking angiotensin II at AT₁ receptors without affecting bradykinin
Why ARBs Are Clinically Important
ARBs provide:
- Excellent BP control
- Renal protection in diabetes
- Mortality benefit in heart failure
- Better tolerability than ACE inhibitors
First choice when ACE inhibitors cause cough or angioedema.
Individual Drugs Explained
Losartan
Key Features
- First ARB introduced
- Shorter half-life compared to others
- Mild uricosuric effect
Uses
- Hypertension
- Diabetic nephropathy
- Hypertension with gout
Exam Pearl
✔ Lowers uric acid levels (unique among ARBs)
Valsartan
Key Features
- Potent AT₁ blocker
- Widely used in cardiovascular disease
Uses
- Hypertension
- Heart failure
- Post-myocardial infarction
Exam Pearl
✔ Commonly used in heart failure guidelines
Candesartan
Key Features
- Long-acting
- Strong receptor binding
Uses
- Hypertension
- Heart failure with reduced EF
Exam Pearl
✔ One of the best ARBs for heart failure
Irbesartan
Key Features
- Long duration of action
- Strong renal protective effect
Uses
- Hypertension
- Diabetic nephropathy
Exam Pearl
✔ Preferred ARB in diabetic kidney disease
High-Yield Comparison Table
| Drug | Duration | Special Feature | Best Known Use |
|---|---|---|---|
| Losartan | Short | ↓ Uric acid | HTN + gout |
| Valsartan | Long | CV benefit | HF, post-MI |
| Candesartan | Long | Strong binding | Heart failure |
| Irbesartan | Long | Renal protection | Diabetic nephropathy |
Clinical Uses of ARBs (Grouped)
Cardiovascular
- Hypertension (first-line)
- Heart failure (ACEI alternative)
- Post-myocardial infarction
Renal
- Diabetic nephropathy
- Proteinuric kidney disease
Special Situations
- ACE inhibitor–induced cough
- Metabolic-friendly BP control
ARBs in Heart Failure (Exam Gold)
Benefits:
- ↓ Mortality (selected agents)
- ↓ Hospitalization
- ↓ Ventricular remodeling
Used when:
ACE inhibitors are not toleratedAdverse Effects (Important)
Common
- Dizziness
- Hypotension (first dose)
Serious (Rare)
- Hyperkalemia
- Acute kidney injury (renal artery stenosis)
- Angioedema (very rare, much less than ACEIs)
Dry cough is uncommon.
Contraindications (Must Remember)
❌ Pregnancy (teratogenic)
❌ Bilateral renal artery stenosis
❌ Severe hyperkalemia
ARBs vs ACE Inhibitors (Exam Favorite)
| Feature | ARBs | ACE Inhibitors |
|---|---|---|
| Cough | Rare | Common |
| Bradykinin | Not increased | Increased |
| Angioedema | Very rare | Possible |
| Mortality benefit | Yes | Yes |
| First choice | If ACEI intolerant | Yes |
Important Exam-Oriented Pearls
- ARBs do not inhibit ACE
- Safe alternative in ACEI-induced cough
- Monitor creatinine & potassium
- Initial mild creatinine rise is acceptable
- Never use in pregnancy
Easy Memory Tricks
- “-sartan = stops angiotensin at receptor”
- “Losar-tan lowers uric acid”
- “Cande-sartan = cardiac protection”
FAQs
1. What is the main action of ARBs?
They block angiotensin II at AT₁ receptors, causing vasodilation and reduced aldosterone.
2. Why don’t ARBs cause cough?
They do not increase bradykinin levels.
3. Which ARB is best for heart failure?
Candesartan and valsartan.
4. Which ARB lowers uric acid?
Losartan.
5. Are ARBs safe in diabetes?
Yes, they are renoprotective.
6. Can ARBs be used in pregnancy?
No, they are contraindicated.
7. What electrolyte imbalance can ARBs cause?
Hyperkalemia.
8. When are ARBs preferred over ACE inhibitors?
When ACE inhibitors cause cough or angioedema.
9. Do ARBs reduce mortality?
Yes, in selected heart failure and post-MI patients.
10. Should renal function be monitored with ARBs?
Yes, creatinine and potassium must be checked.
