Bronchodilator treatment in asthma

Tiotropium in asthma: what is the evidence and how does it fit in?

Despite current therapeutic approaches asthma remains uncontrolled in a significant proportion of patients. Short-acting anticholinergic bronchodilators have a very long history of use in asthma, and recent data confirms the importance of acetylcholine as both a bronchoconstrictor and as a regulator of inflammation and remodeling in the lungs. Data from a comprehensive clinical trial programme, as well as use in primary care, show the efficacy and safety of tiotropium in adults with mild to moderate asthma when it is added to ICS and in severe asthma when it is added to high doses of ICS plus LABA, as well as in adolescents. Tiotropium is cost effective and its benefits are not restricted to particular phenotypes, making it a useful addition to the therapeutic options recommended by the Global Initiative for Asthma (GINA) for people with poorly controlled asthma at steps 4 & 5.

Rapid onset of tolerance to the bronchoprotective effect of salmeterol

INTRODUCTION

Twice-daily inhaled salmeterol for 4 weeks produces marked reduction in its acute bronchoprotective effect against methacholine. This investigation examined the onset of this effect over 5 days, and also assessed cross-tolerance with salbutamol.

SUBJECTS AND METHODS

Ten asthmatic volunteers who were able to withhold beta 2-agonist therapy for 4 weeks before and during the study participated in a double-blind, crossover, placebo-controlled study with two random-order treatment periods: inhaled salmeterol, 50 micrograms twice a day for seven doses, and placebo in similar fashion. Methacholine inhalation tests were done 1 h after doses 1, 3, 5, and 7, and then 24 h after the last dose of the study inhaler 10 minutes after 200 micrograms of salbutamol.

RESULTS

Baseline FEV1 value before doses 3, 5, and 7 of salmeterol (ie, 12 h after salmeterol) was significantly higher than all other (n = 7) values. Twenty-four hours after the last dose of salmeterol, the FEV1 was no different from that during the placebo period. The geometric mean methacholine concentration causing a 20% fall in FEV1 (PC20) after the first dose of salmeterol (6.1 mg/mL) was statistically similar to the value achieved 10 min after salbutamol after the placebo period (8.3 mg/mL), and these were significantly (analysis of variance, p < 0.00005) larger than the second, third, and fourth salmeterol days (3.4 mg/mL, 2.6 mg/mL, 1.9 mg/mL, respectively). The methacholine PC20 10 min after salbutamol measured after the salmeterol period was significantly lower than after placebo (2.3 mg/mL vs 8.3 mg/mL; p < 0.001).

CONCLUSIONS

Tolerance to the acute bronchoprotective effect of salmeterol was significant after the first two doses and progressively increased to the seventh dose. Tolerance to the acute bronchoprotective effect of salbutamol was significant after regular use of salmeterol for seven doses.