Introduction

Bronchodilators are a group of medications used to make a person’s breathing easier. They act by relaxing smooth muscle in the airways (also known as bronchi), making it easier for air to move in and out of the lungs.¹ In turn, this reduces symptoms related to constricted airways, such as shortness of breath, wheezing and chest pain.² Bronchodilators are used in medical conditions where the airways tighten (known as bronchoconstriction). This can be for a number of reasons, and the main conditions they are used to treat are asthma and chronic obstructive pulmonary disease (COPD).¹

Types of bronchodilators

There are two main forms of bronchodilators, short-acting and long-acting methods. The decision around treatment will be made by a medical professional and will depend on the frequency and severity of episodes of breathlessness.¹

Short-acting bronchodilators

Short-acting bronchodilators are used to control the symptoms of sudden shortness of breath. These are sometimes called ‘reliever’ medications and can stop symptoms getting worse and needing further treatment.² As the name suggests, these are for short-term relief, providing symptom improvement for around four hours.³

Salbutamol is the most common short-acting bronchodilator, and is also described as a beta-2 agonists.¹ Beta-2 receptors are found in the walls of the airways and stimulation of these causes the airways to relax. Beta-2 receptors are also found in blood vessels, as well as the heart and explains how salbutamol causes some of its side effects.⁴

Long-acting bronchodilators

Long-acting bronchodilators give patients better overall control of their breathing symptoms, with each administration of medicine providing about twelve hours of symptom relief.³ The most common inhaled long-acting bronchodilator preparations are salmeterol and formoterol, which are long-acting beta-2 receptor agonists. Unlike their short-acting counterparts, these medications are always given alongside steroids.³

Theophylline is another long-acting bronchodilator that can be used in combination with steroids - but owing to its potential side effects, and need for medication levels to be monitored by blood tests, it is used less commonly than other long-acting medication.¹

Antimuscarinic medications

Used more commonly in COPD, antimuscarinic (also known as anticholinergic) medications work by blocking chemicals from interacting with muscarinic receptors in the airways. They can be either short or long-acting, and examples of these include ipratropium bromide and tiotropium.¹

Side effects associated with bronchodilators 

As with all active medications, the mechanism they work by can often cause additional unwanted symptoms, which are described as side effects. Beta-2 receptor agonists, theophylline and antimuscarinic medications all have slightly different side effects as they all work in different ways.⁵

If you are experiencing any side effects that cause you concern or any signs of the serious side effects listed, please seek medical assistance as soon as possible.

Beta-2 receptor agonists

Both short and long-acting beta-2 receptor agonists have the same side effects as they both work in the same way. 

Common side effects include:^1,3,5

• trembling hands 
• Irregular or fast heartbeat (known as palpitations)
• anxiety 
• headaches
• muscle cramps

These side effects normally begin when you start a new medication but will improve and often disappear after a few weeks.⁵ If side effects persist, your medication dose may need adjusting as side effects are more common at higher doses.⁵ 

Rare but serious side effects

Although most side effects of beta-2 receptor agonists improve over time, there are a couple of less common but serious potential side effects to be aware of:^5-7,9

• paradoxical bronchospasm: a rare situation where the airways tighten suddenly again after a bronchodilator has been given 
• cardiac arrhythmia: progressing from a feeling of palpitations, beta-2 receptor agonists can cause more permanent changes to heart rhythm and speed 
• low blood potassium, known as hypokalaemia can have negative effects on the function of the heart, nervous system and muscles
• seizures - a link between asthma attacks, asthma medication and seizures has been widely discussed and needs to be investigated further

Antimuscarinic medications

Common side effects of antimuscarinic medications include:^1,5,8

• dry mouth
• constipation 
• dry cough 
• headache
• nausea 
• dizziness

Less commonly they can also cause:^5,8

• difficulty or discomfort swallowing
• palpitations 
• stomatitis - soreness and inflammation inside the mouth
• problems with passing urine
• paradoxical bronchospasm

Some side effects of antimuscarinic medications are more likely with a pre-existing medical condition causing a tendency for those symptoms already. This can be something like an enlarged prostate or another cause of difficulty in passing urine.¹

Risk of developing or worsening symptoms of glaucoma 

Glaucoma is a serious condition that increases pressure in the eyeball, and if left untreated can cause vision loss. The use of antimuscarinic medications may be advised against if a patient has already been diagnosed with glaucoma.⁸ Additionally there is a risk of developing new glaucoma, especially if nebulised ipratropium bromide (often in combination with salbutamol) accidentally gets into the eyes.¹⁰

Signs to be aware of that you may be developing glaucoma include:¹¹

• eye pain - both in the eye and around the eyeball
• blurred vision 
• developing a red eye 
• seeing rings or ‘halos’ around lights
• headaches
• nausea or vomiting 

If you develop any of these symptoms suddenly whilst taking antimuscarinic medications, it is important to seek emergency medical help.¹¹

Theophylline 

Unlike the other bronchodilators mentioned, theophylline has to be monitored with blood tests to ensure that it is given at an effective dose but does not build up to a toxic level in the body.⁵ 

Side effects of theophylline are similar to those of other bronchodilators and include:⁵

• fast heart rate (tachycardia)
• palpitations
• arrhythmia
• gastric upset - nausea, vomiting and diarrhoea 
• headaches
• sleeping difficulties (insomnia)

Allergic reactions 

Anaphylaxis

Bronchodilators are commonly used in the treatment of serious allergic reactions, and anaphylaxis - however it is possible to have an anaphylactic reaction to salbutamol itself¹² and you can have serious allergic reactions to other bronchodilators. 

Signs of anaphylaxis must be taken seriously and include:¹²

• swelling in and around the mouth, including the lips and the tongue 
• shortness of breath or feeling unable to breathe 
• wheezing 
• difficulty in speaking or swallowing 
• faintness or dizziness 
• confusion 
• loss of consciousness 

Anyone experiencing these symptoms must be seen as a medical emergency. 

Skin reactions

It is possible to develop a skin rash when taking bronchodilator medication, so the development of any new rashes, hives or itching needs to be promptly discussed with a healthcare professional.¹³

Factors influencing side effects

Age

Elderly patients are the age group most at risk of developing side effects with the use of bronchodilators. Both ipratropium bromide and theophylline are to be used with caution in elderly patients, owing to the already increased risks of developing glaucoma or urinary problems for the former⁸ and the very narrow window of safe effectiveness for the latter.¹⁴ These factors will be considered by your healthcare team before prescribing.

Pre-existing conditions 

Owing to the nature of the side effects experienced with bronchodilators, there are certain medical conditions that could be made worse with their use. This does not mean the medication cannot be used, but healthcare professionals will consider whether this is the right medication for you and it is important to let them know of any pre-existing medical conditions you have.

These conditions include:

Beta-2 receptor agonists¹⁴ 

• cardiovascular diseases - such as coronary heart disease, heart failure, peripheral vascular disease and strokes 
• high blood pressure (hypertension)
• diabetes 
• overactive thyroid 
• hypokalaemia
• certain conditions that affect heart rhythm 

Antimuscarinics⁸

• conditions causing difficulty in passing urine 
• benign prostatic hyperplasia 
• previous glaucoma 

Theophylline¹⁵

• cardiac arrhythmias
• cardiovascular diseases
• hypertension 
• epilepsy 
• history of stomach (peptic) ulcers
• thyroid conditions 
• hypokalaemia 

Interactions with other medications^8,14,15 

Many medications have interactions with other medications, and bronchodilators are no different. Therefore it is really important to let your healthcare professional know what medications you take, as well as any medication allergies you may have, so that the safest medication choices can be made for you. 

Monitoring and management of side effects

It is important to attend medical appointments related to your medical condition, as this is your opportunity to discuss your symptoms and the effects that your medication are having, both to treat the condition and regarding side effects. It may be that doses need adjusting, or medications need to be changed to better control your symptoms and reduce side effects. 

Theophylline monitoring 

If you are taking theophylline it is important to follow the blood test monitoring as requested by your healthcare professional. Theophylline is an effective bronchodilator, but side effects worsen as its concentration in the blood increases.¹⁵ Blood theophylline levels are monitored when starting treatment, and if the dose is changed, however the full schedule of tests may depend on your personal medical history.¹⁵

Summary

Bronchodilators effectively ease breathing difficulties associated with conditions like asthma and COPD, but as with all medications, there are associated side effects. Beta-2 agonists produce side effects including palpitations, headaches and muscle cramps but these are generally temporary, improving with exposure. Antimuscarinic medications work in a different way and have common side effects such as developing a dry mouth, constipation and nausea. 

Theophylline, which is often used in combination with other bronchodilators, requires monitoring through blood tests to ensure it is effective without becoming toxic. Side effects such as fast heartbeat and gastrointestinal upset are possible, as well as the risk of developing a serious condition called glaucoma if exposed to the eyes. 

Serious side effects related to bronchodilators include paradoxical bronchospasm, cardiac arrhythmias and low blood potassium, all of which need rapid medical attention. The risk of anaphylactic reaction to bronchodilators is also a possibility and signs of this, including sudden shortness of breath and swelling to the lips, face and tongue must be treated as a medical emergency.

To minimise potential side effects, it is important to attend your medical appointments and, if you are taking theophylline, complete monitoring blood tests. This, alongside being personally vigilant of changes to your own health whilst using bronchodilators will help to avoid unwanted side effects of your medication.