Introduction

Beta-blockers have long been a cornerstone in the management of cardiovascular disease. However, due to their risk of causing potentially life-threatening asthma exacerbation, the prescription of beta-blockers has largely been avoided in people with asthma. So what happens when you have both asthma and cardiovascular disease? This article explores the recent developments on the risks and benefits of beta-blockers in patients with asthma. 

Current medical research suggests that the risk of using non-selective beta-blockers outweighs any potential cardiovascular benefits. Conversely, gradually increasing the dose of selective beta-blockers presents a relatively low risk of severe asthma exacerbation. The use of any beta-blockers in asthma patients must be closely supervised by medical specialists, and the risk of severe respiratory side effects can never be fully excluded.^1,2,3,4

So what are beta-blockers? Why do they pose a risk to patients with asthma? Let’s dive deeper.

How beta-blockers work

Brief explanation of beta-blockers

Beta-blockers are a category of drug, commonly used to treat cardiovascular disease (e.g. abnormal heart rhythms, hypertension, angina) to reduce heart rate and regulate blood pressure.  There are two main types of beta-blockers: selective and non-selective.^2,3

Types of beta-blockers: selective vs. non-selective

The cells in your body have many proteins on their surface known as receptors. These receptors act as a ‘lock and key’ system which initiates a chain of biochemical events. Beta-blockers bind to their specific receptors, known as beta-receptors or beta-adrenergic receptors. There are two main types of beta-receptor: beta-1 and beta-2. Beta-1 blockers are known as selective (alternatively called cardioselective) because the majority of their receptors are found within the cardiovascular system. Beta-2 blockers are known as non-selective because their receptors are found in both cardiac tissue and the respiratory system. 

Mechanism of action on beta-receptors

You’ve most likely heard of adrenaline, a hormone in the body responsible for the ‘fight or flight response’. When adrenaline binds to beta-receptors in your body, it causes your heart rate to increase and expands your airways to prepare you to run away from danger such as a ferocious lion. Beta-blockers work by blocking the action of adrenaline at these receptors, with the main aim of slowing the heart down. So, if beta-blockers alter your heart rate, what do they do to your airways?

Impact on the respiratory system

As beta-2 receptors are present in the respiratory system, beta-2 blockers have the potential to cause bronchoconstriction (narrowing of the airways) as they block the airway dilatory effect of adrenaline. So, if beta-1 receptors don’t affect the airways, why don’t we just use beta-1 blockers in patients with asthma? The concern is that neither beta-1 nor beta-2 blockers are completely specific and can display a phenomenon known as ‘cross-reactivity’. Cross-reactivity means that drugs or hormones which share similarities in structure can exert a mimicking effect at additional receptors to their target receptor. The higher the dose, the less specific beta-blockers are, meaning there could be adverse effects with increasing dosages. Reduced airway diameter in an individual with asthma could also pose a serious health risk.² 

Connection between beta-blockers and asthma

Beta-blockers have historically been contraindicated by the medical community for use in patients with asthma due to their inherent risk of binding to beta-2 receptors and causing potentially life-threatening bronchoconstriction. That said, studies have shown an increased likelihood of the development of cardiovascular disease in later life in patients with asthma. There is also a school of thought within the scientific community that beta-blockers may even exert a positive effect by potentially reducing airway hyperresponsiveness. So, can beta-blockers ever be a viable option for asthmatic patients with heart disease who may strongly benefit from their use?² 

Potential risks for asthma patients

The main risk associated with the use of beta-blockers in asthmatic patients is the development of bronchoconstriction, potentially resulting in a severe and even fatal asthma attack. There have also been concerns surrounding whether beta-agonists, one of the most common drugs found in asthma inhalers (e.g. salbutamol), may be less effective at expanding the airways during an acute asthmatic event if used alongside beta-blockers. Additionally, It has been repeatedly noted in the scientific literature that lung function (measured by forced expiratory volume) initially becomes reduced when a course of beta-blockers is commenced, although this tends to resolve after a few weeks and may be asymptomatic.^1,2,4

Examples of commonly prescribed beta-blockers

Some of the most commonly prescribed beta-blockers, their brand names and their main uses are listed in the table below:

Research and Evidence

Key findings on the beta blockers and asthma relationship

The most recent evidence suggests that the risk of asthma exacerbation is highly unpredictable with the use of non-selective beta-blockers (e.g. propranolol), and this risk outweighs any potential cardiovascular benefits. Conversely, the use of some selective beta-blockers may be appropriate if strongly indicated, and there is a lack of other suitable medication options available. Of the selective beta-blockers on the market, current research suggests bisoprolol and celiprolol generally present the least risk of asthma exacerbation. There have been mixed reports on atenolol, with some studies suggesting it offers the lowest risk of all beta-blockers and other studies observing asthma exacerbations. Doses of any beta-blocker should be increased gradually and closely supervised by a medical specialist.^1,2,3,4

It is very common in the research that a side effect of starting a course of beta-blockers when the patient has pre-existing asthma typically includes a temporary drop in lung function (forced expiratory volume), which usually resolves over a few weeks. There have been no reports of severe asthma attacks or fatalities with the use of selective beta-blockers in the published scientific research. There is sadly one fatality listed on the World Health Organisation database “Vigibase” which may have been associated with a beta-blocker, among other possible causes. Research suggests the rescue effect of inhaled beta-agonist medications (e.g. salbutamol) during asthma attacks may be slightly lessened when used alongside beta-blockers but remains effective, which is encouraging. Furthermore, the Global Initiative for Asthma recently reported that asthmatic individuals admitted to hospitals for a heart attack showed lower mortality rates within 24 hours than those not given beta-blockers.^2,4,5

Inconsistencies and conflicting research

Research on the use of beta-blockers in those with asthma is somewhat limited. There are a number of factors at play which make it challenging to directly compare individual studies. For example, some researchers have not made a distinction between patients with asthma and patients with Chronic Obstructive Pulmonary Disease (COPD). The patient group size studied is often fairly small, which reduces reliability. To minimise risk to the candidates in clinical trials, in some instances, the potential side effects have been buffered by the use of bronchodilators (e.g. ipratropium bromide) which can make it difficult to assess the true effects of the beta-blocker. Research on atenolol has generated mixed outcomes; some studies have named atenolol the safest beta-blocker whereas others have noted bronchoconstriction.^1,4

Practical Recommendations

Guidelines for prescribing beta-blockers in asthma cases

The 2023 report from the Global Initiative for Asthma advises that selective beta-blockers may be used with gradual dose increases on a case-by-case basis under close medical supervision by a specialist. The report states: ‘Asthma should not be regarded as an absolute contraindication to use cardioselective beta-blockers when they are indicated for acute coronary events, but the relative risk and benefits should be considered’. It is also important to note that some eye drops, particularly glaucoma medications, contain beta-blockers which can affect the respiratory system.^1,3

Alternatives and substitutes for asthma patients

Some alternatives to the use of beta-blockers in patients with asthma exist,  however, there are many medications on the market designed to treat cardiovascular disease. You should always seek guidance from a medical professional. 

Future considerations and research directions

There is a school of thought in the scientific community that beta-blockers may even exert a positive effect on the respiratory system by reducing airway hyperresponsiveness. The small amount of research published on the topic has variable outcomes, with some studies noting a small benefit and other studies finding no difference. Further research is required on this topic.^1,2,4

FAQs

Do beta-blockers affect asthma?

Yes, beta-blockers can worsen asthma. Selective beta-blockers are thought to pose a lower risk in patients with asthma than non-selective beta-blockers. Always seek advice from a medical professional.¹

Why are beta-blockers avoided in asthma?

Beta-blockers are often avoided in asthma due to their risk of severe and potentially life-threatening bronchoconstriction (narrowing of the airways).^2,6

Which beta-blocker is best for asthma?

Current research suggests selective beta-blockers offer a relatively low risk of severe asthma exacerbation, particularly bisoprolol and celiprolol.^1,2

Is propranolol okay for asthma?

No. Propranolol should never be used in patients with asthma as it can cause life-threatening bronchoconstriction (narrowing of the airways).¹

What do beta-blockers do?

Beta-blockers are a group of drugs which are commonly used in the treatment of cardiovascular disease (e.g. hypertension, angina and abnormal heart rhythms).³

Summary

• Research on the use of beta-blockers in patients with asthma is limited
• There are no reported fatalities or examples of severe asthma attacks in the published literature with the use of selective beta-blockers. There is one fatality listed on the World Health Organisation (WHO) database which may have been caused by beta-blockers, among other possible causes
• Research suggests that certain selective beta-blockers may be used with a relatively low risk of a severe asthma attack, on a case-by-case basis, using a dose-increasing method
• Inhaler medications (e.g. salbutamol) remain effective when used alongside beta-blockers, although their effect can be slightly reduced
• The risk of using any beta-blockers in patients with asthma can never be fully excluded and patients should always seek medical advice