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Anticholinergic agents for chronic asthma in adults.

BACKGROUND
Anticholinergic agents such as ipratropium bromide are sometimes used in the treatment of chronic asthma. They effect bronchodilation and have also been used in combination with beta2-agonists in the management of chronic asthma.


OBJECTIVES
To examine the effectiveness of anticholinergic agents versus placebo and in comparison with beta2-agonists or as adjunctive therapy to beta2-agonists.


SEARCH STRATEGY
The Cochrane Airways Group asthma and wheeze database was searched with a pre-defined search strategy. Searches were current as of August 2003. Reference lists of articles were also examined.


SELECTION CRITERIA
Randomised trials or quasi-randomised trials were considered for inclusion. Studies assessing an anticholinergic agent versus placebo or in combination/comparison with beta2-agonists were included. In practice, all beta2-agonists were short acting. Short-term (less than 24 hours duration) and longer-term studies were separated; the latter are reported in this review and the former in the review, "Anticholinergic agents for chronic asthma in adults short term".


DATA COLLECTION AND ANALYSIS
Two reviewers independently assessed abstracts for retrieval of full text articles. Papers were then assessed for suitability for inclusion in the review. Data from included studies were extracted by two reviewers and entered into the software package (RevMan 4.2). We contacted authors for missing data and some responded. Adverse effect data were analysed if reported in the included studies.


MAIN RESULTS
The studies analysed were in two groups: those comparing anticholinergics with placebo and those comparing the combination of anticholinergics with short acting beta2-agonists versus short acting beta2-agonists alone. The former group had 13 studies involving 205 participants included in this review, and the latter 9 studies involving 440 patients. Generally methodological quality was poorly reported, and there were some reservations with respect to the quality of the studies. Despite the limited number of studies that could be combined, anticholinergic agents in comparison with placebo resulted in more favourable symptom scores particularly in respect of daytime dyspnoea (WMD -0.09 (95%CI -0.14, -0.04, 3 studies, 59 patients). Daily peak flow measurements also showed a statistically significant improvement for the anticholinergic (e.g. morning PEF: WMD =14.38 litres/min (95%CI 7.69, 21.08; 3 studies, 59 patients). However the clinical significance is small and in terms of peak flow measurements equates to approximately a 7% increase over placebo. The more clinically relevant comparison of a combination of anticholinergic plus short acting beta2-agonist versus short acting beta2-agonist alone gave no evidence in respect of symptom scores or peak flow rates of any significant differences between the two regimes. Again there are reservations with respect to the quality of the information from which these conclusions are drawn.


REVIEWERS' CONCLUSIONS
Overall this review provides no justification for routinely introducing anticholinergics as part of add-on treatment for patients whose asthma is not well controlled on standard therapies. This does not exclude the possibility that there may be a sub-group of patients who derive some benefit and a trial of treatment in individual patients may still be justified. The role of long term anticholinergics such as tiotropium bromide has yet to be established in patients with asthma and any future trials might draw on the messages derived from this review.