Comparison of bronchodilatory properties of transdermal and inhaled long-acting β2-agonists

BackgroundRegular use of long-acting bronchodilators is recommended for symptomatic COPD patients. A transdermal type of β2-agonist, tulobuterol, was recently developed. This agent shows the pharmacokinetic property of a sustained serum concentration for 24 h. However, little has been reported about the bronchodilatory properties of this agent.ObjectivesThe aim of the present study was to compare the bronchodilatory action of transdermal β2-agonist tulobuterol with that of inhaled long-acting β2-agonist salmeterol.MethodsAn open-label, randomized crossover study was performed. Eleven patients with stable COPD were enrolled in the study. Tulobuterol (2 mg/day) or salmeterol (50 μg, twice daily) was administered in a randomized, crossover manner. Forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) and inspiratory capacity (IC) were measured before administration, every 2 h from 12 to 24 h, and at 36 h after the initial administration.ResultsTransdermal β2-agonist tulobuterol showed an improvement in FEV1, FVC and IC after dosing compared with those at baseline. Salmeterol also improved all parameters of FEV1, FVC and IC, and showed a greater improvement compared with the transdermal β2-agonist tulobuterol (p<0.05). The values of the area under the curve (AUC) of FEV1, FVC and IC during the administration of tulobuterol were 2.98±1.05, 1.81±0.98, 0.75±0.85 L h, respectively, and during the administration of salmeterol they were 6.39±1.12, 6.61±1.34, 4.28±0.91 L h, respectively.ConclusionThe transdermal β2-agonist tulobuterol showed bronchodilatory action for at least 24 h by once daily administration. However, its bronchodilatory potency was about three times less than that of the inhaled β2-agonist salmeterol.