A 52-year-old woman with essential hypertension and asthma (on inhaled salbutamol PRN) is prescribed atenolol 50 mg daily for BP control. After 2 weeks, she reports increased frequency of asthma exacerbations and wheezing at rest. What is the most appropriate next step in management?

Explanation

## Clinical Problem Atenolol is a **non-selective beta-blocker** that blocks both β~1~ (cardiac) and β~2~ (bronchial) receptors. In a patient with asthma, this causes unopposed α-adrenergic activity and loss of β~2~-mediated bronchodilation, triggering bronchospasm and asthma exacerbations. ## Key Point: **Non-selective beta-blockers are contraindicated in asthma and COPD.** They cause bronchospasm and are absolutely avoided in these conditions. ## High-Yield: **Beta-blocker selection in asthma/COPD:** | Feature | Non-selective (Atenolol, Propranolol) | Cardioselective (Metoprolol, Bisoprolol) | ISA-containing (Pindolol, Acebutolol) | |---------|----------------------------------------|------------------------------------------|--------------------------------------| | β~1~ blockade | Yes | Yes | Yes | | β~2~ blockade | **Yes (causes bronchospasm)** | Minimal at low doses | Minimal (ISA provides β~2~ agonism) | | Asthma safety | **Contraindicated** | Relatively safe | Safer (ISA provides bronchodilation) | | Hypertension control | Good | Good | Good | ## Management Strategy 1. **Discontinue atenolol immediately** — it is contraindicated in asthma. 2. **Switch to:** - A **cardioselective beta-blocker** (metoprolol, bisoprolol) at low dose, OR - A **beta-blocker with intrinsic sympathomimetic activity** (pindolol, acebutolol), which provides partial β~2~ agonism, OR - An **alternative antihypertensive class** (ACE inhibitor, ARB, calcium channel blocker, thiazide diuretic). ## Clinical Pearl: Cardioselective beta-blockers have relative (not absolute) selectivity for β~1~ receptors. At high doses, they lose selectivity and can still cause bronchospasm. Always use the **lowest effective dose** in asthmatic patients. ## Mnemonic: **"ISA = Intrinsic Sympathomimetic Activity"** — these beta-blockers (pindolol, acebutolol, labetalol) have built-in partial agonist activity, providing some β~2~ stimulation even while blocking β~1~. They are safer in asthma than pure non-selective blockers. ## Why Not the Other Options? - **Option 0 (increase atenolol to 100 mg):** This will worsen bronchospasm; atenolol is contraindicated in asthma regardless of dose. - **Option 2 (add long-acting beta-2 agonist):** While a LABA might provide symptomatic relief, it does not address the root problem—atenolol must be stopped. Adding a LABA to mask the problem is unsafe and delays appropriate management. - **Option 3 (add phosphodiesterase inhibitor):** Phosphodiesterase inhibitors (theophylline, aminophylline) are not first-line asthma therapy and do not reverse beta-blocker-induced bronchospasm.