Angiotensin Receptor Blockers (ARBs) and ACE Inhibitors
The most commonly prescribed ARBs include losartan, valsartan, candesartan, irbesartan, telmisartan, and eprosartan, while common ACE inhibitors include captopril, enalapril, lisinopril, ramipril, and perindopril. Both medication classes are cornerstone treatments for hypertension, heart failure, and diabetic nephropathy by targeting the renin-angiotensin-aldosterone system (RAAS).
Angiotensin Receptor Blockers (ARBs)
ARBs work by selectively blocking the binding of angiotensin II to the AT1 receptor in tissues such as vascular smooth muscle and the adrenal gland 1. This blockade prevents the vasoconstrictor and aldosterone-secreting effects of angiotensin II.
Common ARBs and their dosing:
| ARB | Initial Dose | Maximum Dose | Frequency |
|---|---|---|---|
| Losartan | 50-100 mg | 50-100 mg | Once daily [2] |
| Valsartan | 80-320 mg | 80-320 mg | Once daily [2] |
| Candesartan | 4-16 mg | 32 mg | Once daily [1] |
| Irbesartan | 150-300 mg | 300 mg | Once daily [3] |
| Telmisartan | 40-80 mg | 80 mg | Once daily [2] |
| Eprosartan | 400-800 mg | 800 mg | Once daily [2] |
ACE Inhibitors
ACE inhibitors work by inhibiting the angiotensin-converting enzyme, which catalyzes the conversion of angiotensin I to angiotensin II. This inhibition leads to decreased plasma angiotensin II, resulting in decreased vasopressor activity and decreased aldosterone secretion 4.
Common ACE inhibitors include:
Clinical Applications
Hypertension
Both ARBs and ACE inhibitors are effective first-line treatments for hypertension 2. The European Society of Cardiology/European Society of Hypertension and American College of Cardiology/American Heart Association guidelines recommend either class as initial therapy, often in combination with other agents like calcium channel blockers or diuretics 2.
Heart Failure
ACE inhibitors are generally preferred as first-line therapy for heart failure with reduced ejection fraction (HFrEF), with ARBs recommended for patients who cannot tolerate ACE inhibitors due to side effects like cough 2, 6. Evidence supports the use of captopril, enalapril, ramipril, and trandolapril for reducing mortality in heart failure patients 6.
Diabetic Nephropathy
In patients with diabetic kidney disease, ACE inhibitors or ARBs are recommended as first-line agents, particularly in those with albuminuria (≥300 mg/g Cr) 2. These medications have proven benefits for preventing CKD progression.
Side Effects and Considerations
ACE Inhibitors
- Dry cough (most common side effect)
- Angioedema (rare but serious)
- Hyperkalemia
- Acute kidney injury
- First-dose hypotension
ARBs
- Generally better tolerated than ACE inhibitors
- Lower incidence of cough and angioedema
- Similar risks of hyperkalemia and renal dysfunction
- Contraindicated in pregnancy (category D) 2
Important Clinical Pearls
Combination therapy: The combination of an ACE inhibitor and an ARB should be avoided due to increased risk of adverse effects (hyperkalemia and acute kidney injury) without significant additional benefits 2.
Post-MI management: ACE inhibitors should be started within 24 hours of ST-elevation MI in patients with heart failure, left ventricular dysfunction, or diabetes 7.
Monitoring: For both medication classes, monitor renal function, serum potassium, and blood pressure, especially when initiating therapy or changing doses 3.
Pregnancy: Both ARBs and ACE inhibitors are contraindicated during pregnancy due to risk of fetal harm 3.
Switching between classes: ARBs are an appropriate alternative for patients who experience intolerable cough with ACE inhibitors 8.
By understanding the similarities and differences between these medication classes, clinicians can make informed decisions to optimize patient outcomes in cardiovascular and renal diseases.