Overview of bronchodilators

Respiratory conditions such as asthma and chronic obstructive pulmonary disease (COPD) significantly affect lung function and an individual’s ability to breathe. Bronchodilators are the foundation for the management of respiratory conditions. They are medications that work by helping your airway muscles relax and widening your bronchi so you can breathe more easily.¹  

We can distinguish 3 major types of bronchodilators:

• Beta -agonists, such as salbutamol (Ventolin^®), formoterol (Foradil^®)
• Anticholinergics, such as ipratropium (Atrovent^®), tiotropium (Spiriva^®)
• Xanthines such as theophylline

The preferred method of administration is by inhalation, however some bronchodilators are also available as tablets or capsules.¹ 

This article will help you familiarize yourself with the different types of bronchodilators, identify possible combinations, understand how bronchodilators work, identify their uses and indications, their most common side effects and how to properly take them.

Types of bronchodilators

The most commonly used types of bronchodilators include:

• Beta-agonists
• Anticholinergics
• Xanthines

Short and long-acting bronchodilators

Both beta-agonists and anticholinergic medications are available as short and long-acting. Short-acting beta-agonists are referred to as SABA and long-acting beta-agonists, LABA. Xanthines, however, are only available as long-acting and are administered either orally as tablets, capsules, or syrup, or by injection into the veins.¹

Because of differences in the time needed to start having an effect and the duration of their effects, short and long-acting medications have different indications for use: 

• Short-acting medications act quickly within minutes, and are therefore used in an emergency to rapidly reverse bronchial tightening and facilitate breathing. During an attack, an inhaler is used where the medicine is breathed in through your mouth and delivered to your lungs. The effect of short-acting medications lasts for a couple of hours, with a maximum of six hours.²
• Long-acting bronchodilators do not have an immediate effect and therefore cannot be used during an emergency. However, these medications work longer and are ideal for chronic symptom management. Their effects last for around 12 hours, with newer molecules (indacaterol) controlling symptoms for up to 24 hours.²

The different types of bronchodilators can be viewed in the table below:¹

Beta-agonists

How do they work

This type of bronchodilators works by:¹

• Relaxing the muscles in your airways and relieving the tightening to broaden your bronchi and ease your breathing
• Help clear the thick mucus out of your lungs

Indications for use

Beta-agonists are used in the following cases:

• Asthma (long term management) – The combination of a LABA with an inhaled steroid is considered as the treatment of choice for asthmatic patients.¹
• Acute asthma attacks – SABAs are used in case of emergencies because of their rapid effect
• Exercise-induced asthma
• COPD
• Constriction of the bronchi associated with emphysema and chronic bronchitis

Common side effects

The most common side effects associated with beta-agonist bronchodilators are:

• Tremor of the extremities
• Increased heart rate (tachycardia)

Anticholinergics

How do they work

To understand how anticholinergics work, we first need to highlight what acetylcholine is and what it does. Acetylcholine is a neurotransmitter released by our nerves, which in turn are connected to all our body organs, including the lungs. This signalling molecule acts on receptors that are responsible for airway tightening and mucus secretion. Anticholinergic medications block the effects of acetylcholine, leading to airway relaxation and dilation and reduction in mucus secretion.^3,4

Indications for use

Inhaled anticholinergic medications are used for the management of:¹

• COPD – They are the drugs of choice⁵
• Asthma
• Chronic bronchitis (inflammation and swelling of the bronchi)
• Emphysema

Common side effects

The most common side effects associated with anticholinergic medications include:⁶

• Dry mouth – the most common side effect associated with inhaled anticholinergics
• Blurred vision and visual disturbances if the medication is sprayed into your eyes 
• Dry eyes
• Dry/sore throat 
• Throat irritation 
• Runny nose
• Unusual taste
• Nausea
• Constipation

Less common side effects include:⁶

• Tachycardia, mainly with ipratropium
• Urinary retention or difficulties, mainly with tiotropium

Xanthines - theophylline

Mechanism of action

Theophylline acts via different mechanisms to ease breathing. It relaxes the airway muscles, causing dilation of the bronchi, and it also exerts an anti-inflammatory effect.⁷ 

Indications for use

Despite not being the treatment of choice due to its numerous side effects, theophylline is indicated for the management of:⁷

• COPD
• Asthma – long-term management
• Infant apnea

Common side effects

The development of numerous side effects, even when using the appropriate dose, and the risk of interaction with other medications limit the use of theophylline. The most common side effects associated with theophylline include:⁷

• Nausea
• Vomiting
• Headache
• Increased stomach acid secretion
• Acid reflux
• Irritability
• Lightheadedness
• Dizziness

The administration of high doses of theophylline can cause:⁷

• Seizures
• Convulsions
• Cardiac arrhythmias - problems with your heart rhythm  

Combination bronchodilators

There are many products available on the market, where a single inhaler contains a combination of bronchodilators, or several inhalers are used to achieve the desired combination:¹

Many studies proved that triple therapy with a long-acting beta-agonist, an anticholinergic, and an inhaled steroid is the most favorable method to maximize relaxation and dilation of airway muscles. This combination remarkably benefits, both in the short and long run, individuals suffering from asthma and COPD.¹

Moreover, according to the Global Initiative for Asthma Strategy (GINA), it is recommended that all children aged 6 and above, adolescents, and adults, no matter the severity of their asthma, use a combination therapy of an inhaled steroid with a LABA to manage their asthma instead of using a SABA on an as-needed basis.⁹ 

Administration methods

There are various methods for administering bronchodilators:²

• Orally with tablets, capsules, syrups
• Intravenously, by injecting the medicine directly into your veins
• Inhalation

The inhalation route is the preferred method of administration.² The devices available for delivering the medications are: Metered-Dose Inhalers (MDI), nebulizers, and Dry Powder Inhalers (DPI).²

Metered-Dose Inhalers (MDI) are the most commonly used. They are pressurized handheld canisters containing the medication and a mouthpiece through which the patient inhales the drug. Patients should be instructed on the proper technique when using MDIs to ensure drug delivery to the lungs. Children and elderly find difficulties using this device because it is challenging to coordinate inhalation and activation of the MDI at the same time.

Dry Powder Inhalers (DPI) are devices with a mouthpiece that deliver the medication to the lungs in the form of a powder. Unlike MDIs, DPIs do not require coordination between inhalation and activation of the device. Instead, DPIs are activated once the patient starts breathing. 

Nebulizers are devices that convert liquid medication into mist, which is then inhaled by the patient through a mask or a mouthpiece. It may take up to 15 minutes to complete the treatment using a nebulizer. These devices are beneficial for young children, those with severe asthma, or patients unable to use MDIs or DPIs.

How to properly use a bronchodilator inhaler

For optimal results, it is crucial to follow these step-by-step instructions:

1. Shake the MDI very well
2. Stand or sit up straight and breathe out all the way
3. Make sure that the mouthpiece of the inhaler is placed between the teeth and ensure that the lips are tightly sealed around it
4. Hand-ung coordination: As you start to breath in slowly, press down on the device once
5. Keep breathing in slowly and deeply for 5 seconds
6. Hold your breath for 10 seconds if you can
7. Breathe out slowly

Summary

Bronchodilators are medications used for the management of various respiratory conditions such as asthma, COPD, emphysema and chronic bronchitis. They work by relaxing the airway muscles and dilating your bronchi to facilitate breathing. Bronchodilators are preferably administered by inhalation using an MDI, a DPI, or a nebulizer. We recognize 3 main types of bronchodilators: beta-agonists, anticholinergics, and xanthines (theophylline). 

Beta-agonists and anticholinergics are available as short and long acting, whereas theophylline is only available as long acting. SABAs (salbutamol) act almost immediately and are therefore used during an asthmatic attack, whereas LABAs (formoterol, salmeterol) have a delayed effect and are indicated for the long-term management of asthma. Recent treatment guidelines stress on the use of LABAs for the long-term management of all patients with asthma, in combination with inhaled steroids.

Beta-agonist bronchodilators mainly cause tremors and rapid heart rate as side effects. Inhaled anticholinergics mainly cause local side effects following administration including dry mouth, throat irritation, and unusual taste. Theophylline’s side effects limit its use and render it a second-line treatment option. At low doses, theophylline can cause nausea, vomiting, dizziness, and increased stomach acid secretion. At high doses, seizures, convulsions, and arrhythmias become apparent. 

The choice of bronchodilator, the dose, and the method of administration should be tailored to the needs of each patient, their condition, and severity. Educating patients about the proper use of their bronchodilator device is crucial to maximize benefits and ensure the success of the treatment.