The pharmacological rationale for the use of inhaled tiotropium in asthma

Tiotropium is an inhaled long-acting anticholinergic, with high M3 receptor subtype (M3R) binding affinity, exceedingly half-life at M3R, and functional selectivity. Molecular mechanisms explain binding to muscarinic receptors, long duration of action, kinetic selectivity, and its role as inverse agonist. Tiotropium inhibit airway smooth muscle M3Rs leading to bronchodilation. The intracellular signal transduction pathways for the muscarinic regulation of airway smooth muscle tone are complex. There are many molecular pharmacological reasons for combining this inhaled anticholinergic with beta-2-agonists, and potential non-bronchodilator actions of tiotropium were described. The Respimat SoftMist Inhaler (SMI) is a propellant-free, oral inhalation device, based on an uniblock nozzle system with colliding liquid jets, generating a very fine, slow-moving, long-lasting liquid aerosol. This unique SMI is approved to administer tiotropium bromide in poorly controlled asthma patients. Many pharmacotechnological and pharmacoeducational advantages are discussed, and favourable cost-effectiveness aspects in patients with asthma are mentioned.