A 12-week, randomized, parallel-group, proof-of-concept study of tulobuterol patch and salmeterol inhaler as add-on therapy in adult-onset mild-to-moderate asthma.

Patch formulation of tulobuterol has been used in asthma treatment as a long-acting β2 -agonist (LABA) through sustained skin absorption. Its treatment efficacy, especially in small airways, remains poorly understood. The study aim was to investigate LABA add-on effects of tulobuterol patch (TP) and salmeterol inhaler (SA) on pulmonary function, asthma control and health status. Patients who had adult-onset under-control asthma, despite taking inhaled corticosteroids, were enrolled in a randomized, open-label, parallel-group, proof-of-concept study of 12-week add-on treatment with TP (n=16) or SA (n=17). Spirometry, impulse oscillometry (IOS), exhaled nitric oxide levels, and clinical questionnaires of asthma control, health status (St. George's Respiratory Questionnaire: SGRQ), and symptoms were evaluated every 4 weeks. Add-on treatment of SA significantly improved the spirometric indices of small airway obstruction (forced expiratory flow between 25% and 75% of FVC: FEF25-75 , and maximum expiratory flow at 25% of FVC: MEF25 ) and IOS indices of whole respiratory resistance (resistance at 5 Hz) as compared to TP. In intra-group comparisons, add-on treatment of TP improved the scores of the asthma control test and the total SGRQ, as well as the symptom and impact components of the SGRQ. SA add-on treatment improved FEV1 and IOS parameters of resistance at 20 Hz and reactance at 5 Hz. Neither of the treatments improved exhaled nitric oxide levels. In conclusion, add-on treatment of TP improved asthma control and health status, whereas SA improved pulmonary function measures associated with large and small airway involvement among patients with adult-onset mild-to-moderate asthma.