Asthma Inhalers - Intravenous and Inhaled Terbutaline in the Asthma Treatment

bronchodilatorBronchodilators have been used to treat asthma for many years, but there is still controversy about the best route of administration and the indications for each route. There are many arguments in favor of inhalation therapy, which delivers the bronchodilator to the target organ, and thus keeps the plasma level to the minimum and reduces the likelihood of systemic side effects. Equal bronchodilata-tion with fewer side effects from salbutamol has been shown for the inhaled route by Bloomfield et al in severe acute asthma and by Spiro et al2 in moderately severe asthma.

There are, however, potential disadvantages to the inhaled route, the first being that its effectiveness might suffer with increasing airways obstruction as aerosol penetration and distribution become less efficient. This mechanism was invoked to explain the finding by Williams and Seaton of greater effect with salbutamol using the intravenous (IV) route in patients with severe acute asthma treated by proventil. Another possible objection to the inhaled route is that the aerosol is likely to be deposited preferentially in central and larger airways.

Larsson and Svedmyr have suggested that systemic salbutamol has an effect on small airways as well as on the large airways predominantly involved in the aerosol response. Detroyer et al have further suggested that IV and high-dose aerosol fenoterol have an additional systemic effect of relaxation of retractile elements in the lung parenchyma and alveolar ducts.

This study sets out to examine the effectiveness of a bronchodilator, terbutaline, with respect to its route of administration and site of action both within the airway and, by measurements of gas transport, at the hmg periphery. The study compares dose-response relationships between the two routes of administration in patients with moderately severe asthma to assess the effect of clinically important airways obstruction on bronchodilator response.

Eight patients with bronchial asthma in a stable, moderately severe state were investigated following recovery from a severe attack of asthma. Informed consent was obtained from all patients. All had previously demonstrated at least 20 percent reversibility in their airways obstruction after receiving inhaled bronchodilator. The group consisted of six women and two men. Their mean age was 39 years (range, 19 to 56 years). Seven of the subjects were atopic, as judged by positive skin prick tests to common allergens, and none had chronic bronchitis. In addition to oral and inhaled bronchodilator medication, all were receiving oral corticosteroids, the dose of which was kept constant throughout the study. The mean FEVj on entry to the study was 1.36 L (range, 0.48 to 1.75 L) or 48 percent predicted (range, 15 percent to 67 percent predicted).

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