Comparison of the metabolic responses to alpha-adrenergic stimulation in asthmatics and non-asthmatics after clonidine.

The role of the alpha-adrenergic system in the pathogenesis of asthma is investigated. We administered 150 micrograms oral clonidine to a group of patients with relatively mild asthma and a group of non-asthmatic subjects, and compared their responses by measuring plasma levels of growth hormone (GH), immunoreactive insulin, potassium and glucose. There was no significant difference between the groups in respect of any of these variables, nor was there a significant difference in the blood pressure responses. However, 3 of the asthmatic subjects demonstrated marked hyper-responsiveness of the plasma GH levels after clonidine. It is possible that increased alpha-adrenergic responses may be more frequently demonstrable in a group of severe asthmatics or by means of an alpha-agonist which is more potent and less selective than clonidine. Alternatively, the 3 hyper-responsive individuals may represent a subgroup of asthmatics in whom alpha-adrenergic overactivity is an important pathogenetic mechanism.