Tiotropium bromide

Tiotropium bromide is an anticholinergic bronchodilator that antagonises muscarinic M(1), M(2) and M(3) receptors. It dissociates more slowly from M(1) receptors and, importantly, from M(3) receptors (which are located in bronchial smooth muscle) than from M(2) receptors and subsequently has a long duration of action permitting once-daily administration. In patients with chronic obstructive pulmonary disease (COPD), tiotropium 18microg once daily significantly improved lung function compared with placebo and ipratropium 40microg four times daily in 1-year trials or salmeterol 50microg twice daily in a 6-month study. The incidence of COPD exacerbations decreased and use of rescue medication was lower with tiotropium compared with placebo or ipratropium. There was no evidence of tachyphylaxis during 1-year treatment with tiotropium. Compared with placebo, salmeterol and ipratropium, tiotropium produced significant improvements in patients' perception of dyspnoea and health-related quality of life. Tiotropium is generally well tolerated; dry mouth is the most common drug-related adverse event, occurring in about 10 to 16% of patients in clinical trials.