Influence of an Extension Tube on the Bronchodilator Efficacy of Terbutaline Delivered from a Metered Dose Inhaler

Abstract

Pressurized aerosols of sympathomimetic drugs are widely used in the treatment of bronchial asthma. The efficacy of this form of treatment is diminished in a number of patients by difficulties in coordination between the aerosol actuation and the inhalation. In order to improve the intrapulmonary deposition of terbutaline, an extension tube has been adapted to the regular pressurized aerosol device. In a cross-over randomized study we compared the bronchodilatory effect of increasing doses of terbutaline (250, 500 and 750 μg at 25-min intervals) either delivered by the regular pressurized aerosol device or by the device with the extension tube. The study was performed on 11 adult patients with reversible airways obstruction. Spirometry, body plethysmography and flow volume curves were performed. The onset of the bronchodilatory effect of a single dose of 250 μg terbutaline was more rapid after delivery via the extension tube. The addition of the extension tube caused a significantly higher bronchodilator efficacy of aerosolized terbutaline on the small airways. Our results show that the addition of an extension tube improves the bronchodilator efficacy of terbutaline delivered from a pressurized aerosol.

Device Selection and Outcomes of Aerosol Therapy: Evidence-Based Guidelines

“…Similar findings were reported by Berry et al 61 for inpatients with COPD, but data are lacking for COPD patients treated in the outpatient setting. In an outpatient study of patients with COPD, Pauwels et al 131 compared the use of an MDI and that of an MDI with a valved holding chamber following the inhalation of terbutaline, and reported that the MDI with holding chamber may be more effective than MDI alone. In an outpatient study of patients with asthma or COPD, Dorow and Hidinger et al 132 reported no differences between the use of an MDI and that of MDI with a valved holding chamber.…”

Speed of onset of bronchodilator response to salbutamol inhaled via different devices in asthmatics: a bioassay based on functional antagonism

“…A potential disadvantage of this method is that it is time‐consuming and requires considerable investigator expertise [8]; in addition, it has been questioned whether bronchoprotection represents a situation amenable to the clinical world [8]. Other pharmacodynamic clinical efficacy studies of bronchodilators, including salbutamol, are carried out by measuring bronchodilation in patients with spontaneous [2] or induced bronchoconstriction [3, 5]. Although relatively quick and easy to perform, evaluation of salbutamol‐induced changes in airway calibre in patients with spontaneous bronchoconstriction may be difficult, due to the potentially confounding effects related to the variability of the levels of spontaneous airway narrowing, especially when such variability is not adequately accounted for in patient selection.…”

“…A strong functional antagonism shifts the dose–response curve to the right and may produce differences that are not apparent in bronchodilator studies performed in patients with a mild level of MCh‐induced bronchconstriction. Thus, we believe that the present clinical bioassay, based on the induction of a more marked level of bronchoconstriction (FEV 1 fall −35%) offers a valuable alternative to conventional bronchodilator studies [2] or to studies using bronchoprotection [13, 14, 26].…”

“…The pressurized metered‐dose inhalers (pMDIs) and dry‐powder inhalers (DPIs) are commonly used for administering β 2 ‐adrenergic bronchodilators, such as salbutamol. Studies performed in asthmatic patients with spontaneous [2] or induced bronchoconstriction [3] have shown that salbutamol administration via a DPI or a pMDI in conjunction with a spacer provides faster bronchodilation than the pMDI alone. Whether a difference exists in the speed of the bronchodilator response to bronchodilator agents administered via either a DPI or a pMDI with a spacer in asthmatic patients with natural or induced bronchoconstriction remains to be established.…”