Is Propranolol Cardioselective?
No, propranolol is a non-selective beta-blocker that blocks both β1 (cardiac) and β2 (bronchial, vascular) receptors, which is why it carries significant risk for bronchospasm in patients with asthma or obstructive airway disease. 1
Pharmacologic Classification
Propranolol is explicitly classified as a non-cardioselective β1,2 blocker, meaning it antagonizes beta-adrenergic receptors throughout the body without preferential cardiac selectivity. 2 The FDA drug label confirms that propranolol is a "nonselective, beta-adrenergic receptor-blocking agent" that competes with beta-adrenergic receptor-stimulating agents at all available receptor sites. 1
Clinical Implications of Non-Selectivity
Bronchial Effects
- Because propranolol blocks β2 receptors in bronchial smooth muscle, it causes bronchoconstriction and is absolutely contraindicated in patients with asthma or obstructive airway disease. 3, 4
- Even mild wheezing or chronic obstructive pulmonary disease mandates using a cardioselective agent (such as metoprolol or esmolol) at reduced doses rather than propranolol. 3
Vascular Effects
- β2 receptor blockade in vascular smooth muscle produces vasoconstriction, which can cause cold extremities and may worsen peripheral vascular disease. 3
Cardioselective Alternatives When Non-Selectivity Is Problematic
When propranolol's non-selective blockade poses risk, the ACC/AHA guidelines recommend switching to cardioselective β1-specific agents: 3, 4
- Metoprolol tartrate: 25 mg twice daily, maximum 200 mg twice daily
- Metoprolol succinate (extended-release): 50 mg once daily, maximum 400 mg once daily
- Atenolol: 25–50 mg once daily, maximum 100 mg once daily (requires renal dose adjustment)
Critical Caveat
Even "cardioselective" beta-blockers retain some risk of bronchospasm at higher doses because β1-selectivity is relative, not absolute—all beta-blockers should be used with extreme caution in patients with any history of reactive airway disease. 4
Why Non-Selectivity Matters for Anxiety Treatment
For situational anxiety in adults without cardiac or respiratory contraindications, propranolol's non-selective blockade is actually advantageous because β2 blockade in peripheral tissues helps suppress the somatic manifestations of anxiety (tremor, sweating, palpitations). 4, 2 However, this same non-selectivity makes propranolol unsuitable for any patient with even mild asthma or COPD, where a cardioselective agent would be mandatory if beta-blockade is clinically necessary. 3, 4
Comparison with Cardioselective Agents
The ACC/AHA guidelines note that metoprolol and atenolol are relatively selective β1 blockers, whereas propranolol lacks this selectivity. 3 In patients requiring beta-blockade who have borderline pulmonary function or mild reactive airway disease, starting with a short-acting cardioselective agent such as metoprolol at a reduced dose (e.g., 12.5 mg orally) is preferred over propranolol. 3