During an asthma attack, the airways narrow causing wheezing, coughing and breathlessness. Inhaled short acting beta-2 agonists, such as salbutamol or terbutaline, are commonly used as bronchodilators to relieve these symptoms. They can be used regularly or only when needed and are often used without medical supervision, raising concerns about the possibility of excessive use. The review of trials found little difference between the two methods.
In general, these results support current guidelines, although it has given reassuring evidence against concerns over regular use of inhaled short-acting beta-2 agonists.
Inhaled short-acting beta-2 agonists are the major class of bronchodilators used for relief of symptoms in asthma. There has been concern that excessive uncontrolled use of beta-2 agonists might have contributed to rises in asthma mortality seen in some countries. International consensus guidelines now generally recommend using short-acting beta-2 agonists only for relief of symptoms on an as needed basis.
To assess the effects of using short-acting inhaled beta-2 agonists regularly or only on demand in asthmatic adults and children on indices of asthma control.
Searches were carried out of the Cochrane Airways Group "Asthma and Wheez* RCT" register in 1997, 1999 and 2002. Pharmaceutical companies and researchers with an interest in the area were asked directly for details of any studies that they knew of.
Randomised controlled trials in which the short-acting beta-2 agonist was given regularly in the experimental group, together with an inhaled bronchodilator for relief of symptoms ('rescue use'). The control group consisted of matching placebo inhaled regularly, with an inhaled bronchodilator for 'rescue use'.
Data were extracted and quality assessments were made by both reviewers. Parallel group and cross-over trials were analysed separately. Where possible data were pooled using a fixed effects model.
800 abstracts were identified for the first version and 60 papers were requested for full assessment. In this update 15 studies were added to the 34 trials which met the entry criteria for the first version in 2000. No clinically or statistically significant differences were found in airway calibre measurements. The regular treatment groups required less rescue medication, -0.80 puffs/24 hours (95% CI -0.07 to -1.30) and -0.42 puffs/daytime (95% CI -0.12 to -0.72), and had fewer days with asthma symptoms, -6.7% (95% CI -2.7 to -10.7). There was no significant difference in the odds ratio for the occurrence of at least one major asthma exacerbation either in parallel group or cross over studies.