Effect of Terbutaline on Exercise Capacity and Pulmonary Function in Patients with Chronic Obstructive Pulmonary Disease

Abstract.

The objective of this study was to investigate the effects of a single dose of a β₂-agonist, terbutaline (Bricanyl Turbuhaler®), on resting lung function and exercise capacity in patients with chronic obstructive lung disease. Using a double-blind, placebo-controlled, randomized crossover study and outpatients from a department of pulmonary medicine at a major inner-city hospital, we examined 26 individuals with chronic obstructive lung disease who met the criteria of 40% ≤ FEV₁≤ 70% of predicted, FEV₁/FVC ≤ 70%, and ΔFEV₁≤ 200 ml 20 min after inhalation of 1 mg of terbutaline. The patients inhaled 2.5 mg of terbutaline and matched placebo. At rest, terbutaline caused significant increases in D_LCO, MVV_12sec, and all spirometric indices derived from the flow-volume loop, the increases also being significantly larger than those after inhalation of 1 mg of terbutaline for FEV₁, FVC, and PEF. The peak work rate was unchanged after terbutaline. Oxygen uptake, ventilation, and tidal volume at peak work rate increased significantly, whereas carbon dioxide elimination increased insignificantly. Cumulative oxygen uptake and carbon dioxide elimination during progressive exercise to exhaustion and 10 min of recovery were significantly higher after terbutaline. We concluded that despite significant improvements in resting lung function, inhalation of 2.5 mg of terbutaline did not increase exercise capacity, but it increased cumulative oxygen uptake and carbon dioxide elimination during exercise and recovery, presumably because of a thermogenic effect of terbutaline.