Albuterol was the first |b2-specific bronchodilator to be used for the treatment of asthma. There was initial evidence that regular treatment with this drug over one week improved symptoms and lung function (38). This encouraged clinicians to prescribe albuterol as a regular long-term treatment in order to maximize bronchodilation, and when fenoterol and terbu-taline were introduced they were also used in this manner. Fenoterol became widely used in certain countries such as New Zealand. However, it was apparent in the 1970s that its use was associated with an increase in asthma mortality. It is now known that regular treatment with fenoterol increases AHR and so increases exacerbation rates (39). It is now generally accepted that the increase in asthma deaths in New Zealand were due to the inappropriate use of regular SABA, leading to increased AHR, coupled with the under-prescribing of anti-inflammatory medications such as corticosteroids (40). The combination of these factors meant that some patients were at high risk of severe exacerbations. It is also possible that there were cardiac side effects due to fenoterol overuse during these exacerbations. Consequently, fenoterol was withdrawn from the market in New Zealand and there was a subsequent decrease in asthma mortality. This improvement was due to: (i) more appropriate use of SABA ''as needed'' rather than on a regular basis and (ii) increased prescribing of corticosteroids for anti-inflammatory control.
Clinical trials have subsequently investigated the optimum regime for the long term prescribing of SABA. Large studies have confirmed that regular long-term use of SABA confers no advantages in terms of symptoms and lung function compared to ''as needed'' use (41,42). Furthermore, the regular use of albuterol provides less bronchoprotection against exercise-induced bronchoconstriction (43), and the effects of inhaled allergen challenges (44,45) compared to ''as needed'' use. SABA are generally used for the acute relief of symptoms in mild to moderate asthma, rather than continual maintenance therapy. SABA can also be used as prophylaxis against bronchoconstriction in certain situations, e.g., before exercise.
SABA are used for the initial occasional treatment of mild asthma. Persistent symptoms that require regular SABA use indicate the need for the use of regular anti-inflammatory agents, such as corticosteroids. SABA are then used for the treatment of breakthrough symptoms. The frequency of SABA use can be a guide to the effectiveness of anti-inflammatory treatment, e.g., continued regular SABA use indicates inadequate control of airway inflammation. Patients with moderate to severe asthma who remain symptomatic despite maximal anti-inflammatory treatment often require frequent dosing with SABA for symptom control. In such patients, SABA are not only still used ''as needed,'' but are also taken on a regular basis to minimize symptoms.
The choice of drug in clinical practice often depends on the patient's preference and correct use of a particular inhaler device, e.g., terbutaline is available in a turbohaler while albuterol is not. Although inhalers are used by the majority of asthmatics to administer SABA, nebulizers are often prescribed for patients with more severe disease. Typically, nebulizers are charged with the equivalent of 25 or 50 inhaled puffs (2500 or 5000 vs. 100 mg) of SABA. However, the proportion of the administered dose delivered to the lungs from inhalers (using an MDI and spacer) and nebulizers is similar (46). Nevertheless, some patients prefer nebulizers for ease of use and perhaps psychological comfort.
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If you suffer with asthma, you will no doubt be familiar with the uncomfortable sensations as your bronchial tubes begin to narrow and your muscles around them start to tighten. A sticky mucus known as phlegm begins to produce and increase within your bronchial tubes and you begin to wheeze, cough and struggle to breathe.