Oral bronchodilators are medicines that are used to treat breathing problems in people with asthma and other lung-related problems such as chronic obstructive pulmonary disease. There are two types of oral bronchodilators available to prescribe in the UK. These are beta2 agonists (salbutamol, bambuterol and terbutaline) and methylxanthines (theophylline and aminophylline). Oral bronchodilators help to relieve symptoms such as coughing, wheezing and shortness of breath, by opening up the air passages in the lungs so that air can flow into the lungs more freely.
What are oral bronchodilators?
Oral bronchodilators are medicines that are used to treat breathing problems in people with asthma and other lung-related problems such as chronic obstructive pulmonary disease (COPD). They help to relieve symptoms such as coughing, wheezing and shortness of breath.
There are two types (groups) of oral bronchodilators available to prescribe in the UK. These are:
- Beta2 agonists (salbutamol, bambuterol and terbutaline).
- Methylxanthines (theophylline and aminophylline).
Aminophylline is a 2:1 mixture of theophylline and ethylenediamine. Ethylenediamine is used to improve how well theophylline dissolves in water. Oral bronchodilators are available as capsules, tablets and oral liquids. Aminophylline is also available as an injection; this is usually given in hospital. They all come in various different brand names.
Two other bronchodilators called ephedrine and orciprenaline are also licensed in the UK. However, they are very rarely used nowadays to treat breathing problems because they can cause serious side-effects such as an irregular heartbeat.
Bronchodilators are also available as inhaled medicines. These are much more commonly used bronchodilators. However, the rest of this leaflet only discusses the use of oral bronchodilators (that is, bronchodilators that you take by mouth as capsules, tablets or liquids). See also the separate leaflets called Inhalers for Asthma and Inhalers for COPD.
How do oral bronchodilators work?
The word bronchodilator means to widen (dilate) the bronchi. Bronchodilators work by opening the air passages (bronchi and bronchioles) wider so that air can flow into the lungs more freely. The two different types of oral bronchodilators work in a slightly different way to one another.
Work by stimulating receptors called beta2 receptors in the muscles that line the air passages. This relaxes these muscles, which can make the air passages widen which can make it easier to breathe.
It is still not known exactly how these medicines work. However, it is thought that they stop a substance in the body, called phosphodiesterase, from working. This then relaxes the muscles in the air passages, leading to easier breathing. Unfortunately, when phosphodiesterase is blocked this can lead to other effects such as low blood pressure, a fast heartbeat, headache and nausea.
When are they usually prescribed?
As stated above, these medicines are usually prescribed for people who have lung-related problems that mean they have difficulty breathing. They are most commonly prescribed for people who have asthma or COPD. Most people with asthma do not need an oral bronchodilator. This is because inhalers usually work well.
In some cases a tablet (liquid form for children) form of beta2 agonist is prescribed, especially for young children and for the elderly. However, inhaled bronchodilators are more effective and have fewer side-effects.
Methylxanthines are normally prescribed for people who have stable COPD rather than in an acute exacerbation. Aminophylline injection is sometimes prescribed by hospital doctors if you have a very severe asthma attack.
How should I take oral bronchodilators?
Salbutamol tablets are normally taken three or four times a day. Terbutaline is usually taken three times a day, whereas bambuterol is taken once a day at bedtime (adults only).
Theophylline tablets and capsules may be taken either once a day or twice a day, depending on which brand your doctor has prescribed. It is important always to stick to the same brand of theophylline. This is because, the amount of theophylline absorbed by the body varies greatly between brands. If you start taking a different brand to the one you normally have, you may be having too much or too little theophylline. Aminophylline is usually taken twice a day.
What dose should I take?
The dose prescribed usually depends on how well you respond to treatment and how old you are. Normally your doctor will start off with a low dose and increase this (if necessary) over a number of weeks until you find the right dose.
Getting the dose of theophylline and aminophylline just right can be tricky. The body breaks down (metabolises) theophylline in the liver. This metabolism varies from person to person. The blood levels of the medicine, therefore, can vary enormously. This is particularly the case in smokers, people with liver damage or impairment and in heart failure. In some conditions, the breakdown is reduced and blood levels increase. In other conditions, the breakdown is increased and so blood levels of theophylline fall. This is very important, as the toxic (dangerous) dose for theophylline is only just above the dose that is needed for the medicine to work well. When you first start treatment with one of these medicines your doctor will take some blood tests to make sure you are getting the right amount of medicine. This blood test measures how much theophylline is in your blood. Ideally the amount of theophylline in the blood is kept between 10 and 20 mg/L. Once you are settled on treatment your doctor may do more blood tests from time to time to check how much theophylline is in your blood.
What is the usual length of treatment?
If bronchodilators help your symptoms then they are usually prescribed long-term. Your doctor or practice nurse will monitor your breathing regularly and review your need for these medicines.
What are the possible side-effects?
As with all medicines, oral bronchodilators have a number of side-effects. Listed below are some of the more common side-effects:
- Beta2 agonists - common side-effects include: fine tremor (for example, shaking of the hands), nervous tension, headache, muscle cramps and the sensation of having a 'thumping heart' (palpitations).
- Methylxanthines - these commonly cause side-effects such as: palpitations, feeling sick (nausea), headache and occasionally abnormal irregular heartbeat (arrhythmia) or even fits (convulsions).
For a more detailed list see the leaflet that came with your medicine.
Can I take other medicines?
There are very few medicines that cannot be taken with salbutamol. However, there are quite a few medicines that can affect theophylline. For example, cimetidine, ciprofloxacin, erythromycin, fluvoxamine, and St John's wort can increase the amount of theophylline in your blood. In addition, some medicines such as phenytoin, carbamazepine, or rifampicin decrease the amount of theophylline in your blood.
If you start taking a medicine that can interfere with the amount of theophylline in your blood, your doctor may need to increase or decrease your theophylline (or aminophylline) dose.
If you take a methylxanthine such as theophylline or aminophylline, always ask your pharmacist for advice regarding which medicines it is safe to take.
If you are a smoker and decide to stop smoking, you may need to have your dose of theophylline or aminophylline reduced. This is because people who smoke break this medicine down quickly (compared with people who do not smoke) and usually need a higher dose, compared with people who do not smoke. Your practice nurse or pharmacist will advise.
Can I buy oral bronchodilators?
No - you cannot buy oral bronchodilators; you need a prescription to obtain these medicines.
Who cannot take oral bronchodilators?
The vast majority of people are able to take an oral bronchodilator.
How to use the Yellow Card Scheme
If you think you have had a side-effect to one of your medicines, you can report this on the Yellow Card Scheme. You can do this online at the following web address: http://yellowcard.mhra.gov.uk
The Yellow Card Scheme is used to make pharmacists, doctors and nurses aware of any new side-effects that your medicines or any other healthcare products may have caused. If you wish to report a side-effect, you will need to provide basic information about:
- The side-effect.
- The name of the medicine which you think caused it.
- The person who had the side-effect.
- Your contact details as the reporter of the side-effect.
It is helpful if you have your medication and/or the leaflet that came with it with you while you fill out the report.
Dr Colin Tidy
Prof Cathy Jackson