Labetalol and Carvedilol Are NOT Cardioselective Beta Blockers
Both labetalol and carvedilol are non-selective beta blockers that block both beta-1 and beta-2 adrenergic receptors, and they additionally possess alpha-1 blocking properties—they are definitively NOT cardioselective. 1
Beta Receptor Selectivity Classification
Non-Selective Beta Blockers (Block Both Beta-1 and Beta-2)
- Labetalol and carvedilol are explicitly classified as having "None" for beta-1 selectivity in ACC/AHA guidelines 1
- Both agents are listed as "combined alpha and beta blockers" with non-selective beta-blocking activity 1
- The FDA drug label for carvedilol confirms it is a "nonselective β-adrenergic blocking agent with α1-blocking activity" 2
- The FDA drug label for labetalol describes it as providing "nonselective, competitive, beta-adrenergic blocking activity" combined with "selective, competitive, alpha1-adrenergic blocking" 3
True Cardioselective (Beta-1 Selective) Agents
The following agents ARE cardioselective and preferentially block beta-1 receptors 1:
- Metoprolol (both tartrate and succinate formulations)
- Atenolol
- Bisoprolol
- Betaxolol
- Esmolol (intravenous)
- Nebivolol (cardioselective with vasodilatory properties)
Clinical Implications of Non-Selectivity
When Beta-1 Selectivity Matters
Patients with reactive airway disease or COPD should receive beta-1 selective agents (like metoprolol or esmolol) rather than non-selective agents (like labetalol or carvedilol) because non-selective beta blockade causes beta-2 receptor antagonism, leading to bronchoconstriction 1
- Beta-2 receptors are located primarily in vascular and bronchial smooth muscle 1
- Inhibition of beta-2 receptors produces vasoconstriction and bronchoconstriction 1
- Guidelines specifically recommend: "initially, low doses of a beta-1–selective agent should be used" in patients with significant COPD or reactive airway disease 1
- If concerns exist about beta blocker intolerance, "initial selection should favor a short-acting beta-1–specific drug such as metoprolol or esmolol" 1
Unique Properties of These Non-Selective Agents
The alpha-1 blocking activity of labetalol and carvedilol provides additional vasodilation that distinguishes them from other non-selective beta blockers (like propranolol or nadolol) 1, 4
- The alpha-to-beta blockade ratio for labetalol is approximately 1:3 orally and 1:7 intravenously 3, 5
- Carvedilol has approximately 7 times higher potency for beta receptors than alpha receptors 6
- This combined blockade reduces peripheral vascular resistance while providing beta blockade 3, 4, 5
- In heart failure, carvedilol showed greater benefit than the beta-1 selective agent metoprolol, likely due to its "mixed beta-blocking and alpha-adrenergic-blocking effects" 1