Combinations of bronchodilators often result in greater bronchodilation than do single agents. Possibly this is partly due to the fact that most clinical studies are performed with recommended rather than optimal doses of the agents. An additional consideration may be that anticholinergic, adrenergic, and methylxanthine agents work by different mechanisms, affect different-sized airways, and have different pharmacodynamic and pharma-cokinetic properties, their combination is thus rational. No unfavorable interactions between these three classes of agents have been reported, so the greater bronchodilation achieved by their combination is achieved without increasing the risk of side effects. In practice, it is common to use two or even all of these agents concurrently in airways obstruction, particularly when severe. Fixed combinations in a single-delivery device are more convenient for patient's use and thus likely to lead to greater compliance.
Single MDIs combining different classes of inhaled bronchodilators have been in use since at least the 1950s. Fixed combinations of ipratropium and the p2-adrenergic agent fenoterol (Berodual® and DuoVent®) have been in wide use outside the United States since the 1980s. The combination of ipratropium and albuterol, both in recommended dosage (Combivent®), has been available for a decade. Clinical trials with this combination in patients with COPD (64-66) suggest that it possesses all the advantages mentioned above, and has been found to be cost-effective (67). Bronchodilation is greater during the first four to five hours after administration, but not much prolonged over that achieved by single agents, and no increase in side effects is incurred. A combination solution of ipratro-pium bromide and albuterol for nebulization (DuoNeb®) produced similar results (68). The co-administrations of ipratropium with salmeterol (69) or formoterol (70,71) have also been explored.
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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.