Influence of slow-release terbutaline on the circadian variation of catecholamines, histamine, and lung function in nonallergic patients with partly reversible airflow obstruction.

In order to study the mechanism underlying early morning dyspnea in patients with chronic airflow obstruction, the relation was assessed between the diurnal variation of FEV1, plasma and urinary catecholamines, and urinary histamine (metabolites) in eight nonallergic patients (mean age, 53 years). These parameters were measured both after administration of placebo and slow-release terbutaline tablets during 1 week. The fall in FEV1 at 4 A.M. coincided with a fall in both plasma and urinary epinephrine levels, whereas no correlation between pulmonary function and norepinephrine levels was observed. Histamine and N tau -methylhistamine excretion were found within the normal range without a circadian rhythm, suggesting no important role for histamine in the occurrence of early morning dyspnea in this nonallergic patient group. Administration of slow-release terbutaline during 1 week prevented the nocturnal fall in FEV1. Terbutaline treatment suppressed plasma and urinary levels of epinephrine significantly without any effect on norepinephrine. We conclude that epinephrine appears to be an important factor in the regulation of the bronchial smooth muscle tone in patients with early morning dyspnea.