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Preventers control the swelling and inflammation in the airways, stopping them from being so sensitive and reducing the risk of severe attacks.

Not everyone with asthma will be prescribed preventer medicine.

The protective effect builds up over a period of time so they need to be taken every day (usually morning and evening) even when you are feeling well.

Preventers do not give immediate or quick relief when you are breathless but instead they reduce long-term inflammation. Preventer inhalers usually contain a low dose of steroid medicine.

There are several kinds of preventers, but they all work in the same way. You will be started on an appropriate level of treatment to get your symptoms under control; once this has been achieved the treatment will be reduced to the lowest possible dose.

When are preventers prescribed?

You should be prescribed a preventer if you:

  • are breathless, cough or have a tight chest during everyday activities three or more times a week
  • need to use your reliever inhaler three times a week or more
  • have sleep disturbed by cough or chest tightness each week
  • have bad attacks of breathlessness when you have a chest infection or are in a smoky atmosphere.

What will my preventer do for me?

As the protective effect of the steroid builds up, you will be less likely to have asthma attacks. You will be less likely to be breathless during the day and night and you will not need to use your reliever inhaler as often.

Why is my reliever inhaler not enough?

Reliever inhalers relax your airways, which help breathlessness, but they do not remove airway inflammation. As well as the relaxing effect of a reliever inhaler, you need the anti-inflammatory effect of a preventer. Once airways are less inflamed they are less sensitive to triggers such as cigarette smoke and viral infections.

How long will it take to work?

It may take up to 14 days for your preventer medicine to reduce inflammation and mucus in your airways.

Don't stop taking it if nothing much happens for a few days. Gradually, chest tightness, night cough and wheeze should become less. You should notice that you need to use less reliever inhaler.

When should I see my doctor or asthma nurse again?

Your doctor or asthma nurse will probably want to see you within a month after you start using a preventer. They will be able to adjust your medicines if your symptoms are not decreasing. Or, if your preventer works well for you, you may be able to cut down on the number of puffs you take each day, or the strength of the medicine.

Do I really need to take my preventer every day?

Yes. To work properly, preventers need to be taken every day, usually morning and evening, even if you are feeling well. The protective effect of the preventer medicine builds up gradually.

Once this protection is working, occasionally forgetting to take your inhaler will usually not have bad effects. But forgetting or stopping for several days at a time will mean your protection begins to disappear. If you stop using your preventer, chest infections are more likely to bring on an asthma attack.

Will my preventer medicines change?

Yes. It is likely that you will have to change your medicines from time to time.

If your asthma gets really bad, you may need to increase the dose you take. Or you may need a short course of steroid tablets as well as your regular preventer.

When you begin taking preventer medicine, your doctor or asthma nurse may want you to take a higher dose each day. This will get your asthma under control quickly. As your symptoms improve, you may be able to take fewer daily puffs or move to a lower strength inhaler.

If your regular preventer medicine and occasional use of your reliever inhaler does not control your asthma you should make an appointment with your doctor or asthma nurse to have a review.

Long-acting reliever inhalers

As the name suggests, long-acting relievers work in a similar way to your usual reliever inhaler but the effects last for longer - around 12 hours instead of four. Long-acting relievers open up the airways by relaxing the muscles that surround the airways and are generally taken twice a day. Long-acting reliever inhalers should only be used if you are also taking a steroid preventer inhaler. They are an add-on therapy and should not be used on their own to treat asthma.

Combination inhalers

Combination inhalers contain both a long-acting reliever and a steroid preventer. They should be taken regularly, every day as prescribed, even when you are feeling well.

One of the combination inhalers available can now be used both as a preventer and as your reliever. This is because the long acting reliever medicine in this particular combination inhaler has been shown to relieve asthma symptoms as quickly as short-acting relievers. If you have been prescribed a combination inhaler your doctor or asthma nurse should explain to you how it works.

Leukotriene receptor antagonists

These are medicines that are sometimes referred to as 'preventer' tablets, but unlike your preventer inhaler they do not contain steroid medicines. If your doctor or asthma nurse prescribes you preventer tablets, they should be taken in addition to your usual preventer inhaler.

Preventer tablets work by blocking one of the chemicals that is released when you come into contact with an asthma trigger. They may be particularly effective if your asthma is triggered by exercise or allergies. Preventer tablets are usually taken once or twice a day, even when you are feeling well. However, if you are prescribed preventer tablets, your doctor or asthma nurse should discuss with you how often you need to take them. If they have no effect after four to six weeks, then they are probably not the right medicine for you and you should discuss other treatment options with your doctor or asthma nurse.


Theophylline works by relaxing the muscles that surround the airways. It is usually prescribed as a tablet and is generally taken twice a day. It is important that your doctor gives you the dose of this medicine that is exactly right for you, so you should have regular blood tests to monitor the levels of theophylline in your blood. If your blood level of theophylline is too low the medicine won't work, but if it is too high it can cause unpleasant side effects. If you are taking other medicines, these can affect how well theophylline works. Smoking can also stop theophylline from working the way it should.

Ensure you tell your doctor if you are taking prescribed, complementary or over the counter medicines or if you are exposed to cigarette smoke. Different brands of theophylline may provide different doses so it is important to check that your pharmacist gives you the exact brand that you have been prescribed. You should continue to take the same brand unless your doctor discusses a change with you.


Xolair is the first in a new generation of drugs for severe, difficult-to-control allergic asthma, where patients have an oversensitive immune system. It is a steroid free medication which is given by injection every two or four weeks.

Xolair has been shown to reduce emergency admissions to hospital, improve lung function and reduce asthma symptoms. It is suitable for people over the age of 12 years who have moderate to severe persistent asthma symptoms despite taking regular inhaled corticosteroid treatment.

There are 520,000 people with asthma in the UK for whom existing treatments do not work, and Xolair can provide a solution for around 6,000 of them.

Xolair is only available through respiratory clinics within the hospital following an assessment which will include a blood test to see if it will be suitable. People with persistent asthma symptoms and who have had two or more hospital admissions for asthma over a year may be considered for Xolair.