Is metoprolol (beta-blocker) safe for patients with asthma?

Metoprolol in Asthma: Safety and Clinical Use

Metoprolol can be used cautiously in patients with asthma when cardiovascular indications are compelling, but it requires starting at very low doses under close medical supervision with bronchodilators readily available, and asthma remains a relative—not absolute—contraindication. 1

Key Clinical Guidance

Relative vs Absolute Contraindication

• Beta-blockers are only relatively contraindicated in asthma, not absolutely contraindicated, according to the 2016 European Society of Cardiology guidelines. 1
• The historical absolute contraindication was based on small case series from the 1980s-1990s using very high initial doses in young patients with severe asthma. 1
• Cardioselective beta-1 blockers (bisoprolol, metoprolol succinate, or nebivolol) are strongly preferred over non-selective agents. 1

FDA Warning and Pharmacology

• The FDA label explicitly warns that patients with bronchospastic disease should, in general, not receive beta-blockers, including metoprolol. 2
• However, because of its relative beta-1 selectivity, metoprolol may be used in patients with bronchospastic disease who do not respond to or cannot tolerate other antihypertensive treatments. 2
• Beta-1 selectivity is not absolute—at higher plasma concentrations, metoprolol also inhibits beta-2 receptors in bronchial musculature. 2

Practical Implementation Algorithm

When Metoprolol is Considered Essential:

1. Start with the lowest possible dose (use smaller doses three times daily rather than larger doses twice daily to avoid higher peak plasma levels). 2

2. Initiate under direct medical observation with close monitoring for signs of airway obstruction including wheezing, shortness of breath, and lengthening of expiration. 1, 3

3. Ensure bronchodilators (beta-2 agonists) are readily available or administered concomitantly before starting metoprolol. 2, 3

4. Monitor for respiratory deterioration: Acute exposure to selective beta-blockers causes a mean FEV1 decline of −6.9%, with one in eight patients experiencing ≥20% fall in FEV1. 4

Risk Stratification

• Severe asthma is a stronger contraindication: Patients with severe or poorly controlled asthma should be referred to specialist care before initiating beta-blocker therapy. 1
• Older patients with mild asthma may tolerate cardioselective beta-blockers better, as true severe asthma is less common in this population. 1
• Non-selective beta-blockers (including propranolol, timolol eye drops) should be absolutely avoided in asthmatic patients, as risk outweighs benefits. 1, 5

Evidence on Bronchospasm Risk

Acute Effects

• Metoprolol causes significantly less reduction in FEV1 and FVC compared to non-selective beta-blockers like propranolol at equivalent beta-1 blocking doses. 2
• Beta-2 agonist rescue therapy is partially effective for beta-blocker-induced bronchospasm, but response is attenuated by −10.2% with selective agents. 4
• A dose-response relationship exists—higher doses carry greater bronchospasm risk. 4

Clinical Tolerance

• In one study of 20 asthmatic patients, metoprolol caused only very slight decreases in peak flow values, and five patients with severe asthma experienced subjective improvement (reduced dyspnea, improved general status) due to heart rate control. 6
• However, individual responses are unpredictable—in another study, 7 of 15 asthmatic patients could not tolerate even low cumulative doses of metoprolol (average maximum 26.8 mg). 7

Critical Caveats

• Symptoms of bronchospasm affect approximately 1 in 33 patients with selective beta-blockers versus 1 in 13 with non-selective agents. 4
• Specialist supervision is recommended when prescribing beta-blockers to asthmatic patients, particularly those with previous beta-blocker intolerance, severe asthma (Class III/IV), or suspected bronchial disease. 1, 8
• Alternative cardiovascular medications should be considered first: For rate control in atrial fibrillation, consider non-dihydropyridine calcium channel blockers (diltiazem, verapamil); for hypertension, consider calcium channel blockers, ACE inhibitors, or ARBs. 8

When to Avoid Completely

The FDA lists absolute contraindications as: 2

• Asthma bronchiale (severe, uncontrolled)
• Severe bronchial disease
• Symptomatic bradycardia or hypotension

Recent evidence confirms that cardioselective beta-blockers in low doses are not associated with significantly increased risk of moderate or severe asthma exacerbations in most patients, but individual risk assessment remains essential. 5