ARBs Can Be Safely Used in Patients with Acute Irritant-Induced Bronchospasm and Hypertension
Yes, ARBs are safe and recommended for asthmatic patients and those with bronchospasm, particularly when ACE inhibitors cannot be tolerated, as ARBs do not inhibit kininase and are associated with a much lower incidence of cough and respiratory side effects. 1
Why ARBs Are Safe in Bronchospasm
ARBs produce hemodynamic and neurohormonal effects consistent with renin-angiotensin system blockade without the respiratory side effects of ACE inhibitors. 1 This is mechanistically important because:
- ARBs do not inhibit kininase (ACE) and therefore do not affect bradykinin metabolism, which is the primary mechanism behind ACE inhibitor-induced cough and bronchospasm 2
- ACE inhibitors are associated with cough in 12.3% of patients and bronchospasm in 5.5% of patients, with a relative risk of 2.39 for bronchospastic reactions compared to control medications 3
- ACE inhibitor-induced cough is specifically associated with underlying bronchial hyperreactivity, with 8 of 9 coughers demonstrating bronchial hyperreactivity on methacholine challenge 4
Practical Implementation Strategy
Start with low doses and titrate upward, with careful monitoring of blood pressure, renal function, and potassium levels within 1-2 weeks of initiation. 1
Recommended ARB Options and Dosing:
- Candesartan: 4-8 mg once daily initially, maximum 32 mg once daily 1
- Losartan: 25-50 mg once daily initially, maximum 50-100 mg once daily 1
- Valsartan: 20-40 mg twice daily initially, maximum 160 mg twice daily 1
Blood Pressure Targets:
- Target office BP to 130 mmHg systolic, and lower if tolerated, but not <120 mmHg 5
- Diastolic BP should be <80 mmHg but not <70 mmHg 5
- In older patients (≥65 years), target SBP range of 130-140 mmHg if tolerated 5
Evidence for Equivalent Efficacy
ARBs provide equivalent cardiovascular protection to ACE inhibitors across multiple indications:
- In heart failure with reduced ejection fraction, studies have shown equivalence of benefit between ACE inhibitors and ARBs (candesartan or valsartan), with both classes effective in lowering BP (Class I, Level of Evidence A) 5
- In hypertension, there is no difference in efficacy between ARBs and ACE inhibitors regarding all-cause mortality, cardiovascular mortality, myocardial infarction, heart failure, stroke, and end-stage renal disease 6
- ARBs achieve trough BP lowering of approximately -8/-5 mmHg at maximum recommended doses 7
Critical Safety Monitoring
Use caution in patients with:
- Low systemic blood pressure 1
- Renal insufficiency (avoid if serum creatinine ≥2.5 mg/dL in men or ≥2.0 mg/dL in women) 5
- Elevated serum potassium (>5.0 mEq/L) 5, 1
Monitor within 1-2 weeks: blood pressure, renal function, and serum potassium levels, particularly in patients with pre-existing renal insufficiency or diabetes mellitus. 2
Important Caveats
While ARBs are alternatives for patients with ACE inhibitor-induced angioedema, caution is advised as approximately 2-10% of patients have also developed angioedema with ARBs due to cross-reactivity. 1, 2 However, this risk is substantially lower than continuing an ACE inhibitor in a patient with bronchospasm.
Avoid routine combined use of an ARB with both an ACE inhibitor and aldosterone antagonist, as this combination increases risks of hypotension, renal dysfunction, and hyperkalemia. 1
Combination Therapy Considerations
Evidence strongly supports the inclusion of a RAAS blocker (ARB) in patients with diabetes and hypertension. 5 BP control often requires multiple drug therapy with a RAAS blocker and a calcium channel blocker or diuretic, with dual therapy recommended as first-line treatment. 5
The combination of an ACE inhibitor and an ARB is not recommended due to increased adverse events without additional benefit. 5