Tiotropium bromide

Tiotropium bromide is an anticholinergic bronchodilator that antagonises muscatinic 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 18mug once daily significantly improved lung function compared with placebo and ipratropium 40mug four times daily in 1-year trials or salmeterol 50mug 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.