Effect of an α-Adrenergic-Blocking Drug on Bronchodilation and Protection in Provocation Tests in Patients with Chronic Obstructive Airways Disease, Bronchial Asthma, and in Non-Responders

Abstract

The interplay of α-adrenergic receptors in the function of human bronchial muscle has been elucidated in recent papers. The present study was performed to evaluate the clinical significance of phentolamine in the treatment of airway obstruction. In 12 patients with reversible airway obstruction (8 with allergic bronchial asthma, 4 with chronic obstructive airways disease (COLD), the effect of combined administration of phentolamine and isoprenaline on bronchodilation was analyzed in a controlled cross-over study. Phentolamine was administered in a random order before (one day) or after (another day) isoprenaline. Airway resistance (Raw) decreased insignificantly after phentolamine, but decreased markedly after isoprenaline. Pretreatment with phentolamine did not intensify the bronchodilating effect of isoprenaline. In 4 subjects with COLD being non-responders to isoprenaline, administration of phentolamine prior to isoprenaline did not effect the bronchial reactivity. From this it is concluded that phentolamine does not reestablish the sensitivity of β-receptors in patients with COLD. In subjects, the protective effect of phentolamine was examined in allergene and acetylcholine challenge and compared to isoprenaline. In all the subjects, suffering from allergic bronchial asthma, phentolamine did not demonstrate any protective effect, whereas isoprenaline did. Though imbalance between α- and β-adrenergic receptors is suggested to play a role in airway obstruction, especially in allergic bronchial asthma, the present results point out that α-receptor-blocking drugs seem to be less suited in daily treatment of airways obstruction.