Tiotropium bromide (Spiriva, BA679BR, Boehringer Ingelheim) is a novel inhaled, long-acting anticholinergic bronchodilator that is employed as a once-daily maintenance treatment for patients with chronic obstructive pulmonary disease (COPD). Like ipratropium bromide, tiotropium bromide is a quaternary ammonium derivative that binds to muscarinic receptors. However, although tiotropium binds with high affinity to muscarinic receptors of M1-, M2- and M3-subtypes, it dissociates very slowly from M1- and M3-receptors but more rapidly from M2-receptors, thereby giving it a unique kinetic selectivity. To date, the short-acting anticholinergic agents ipratropium and oxitropium bromide have been extensively employed as bronchodilator therapy for patients with COPD. Indeed, the Global Initiative for Chronic Obstructive Lung Disease (GOLD) strategy emphasises the role of bronchodilators in symptomatic management of all stages of COPD. It is encouraging that tiotropium given once daily from a dry powder inhaler at 18 g has been shown to cause greater improvement in lung function and reduction in symptoms than ipratropium bromide given four times daily. Furthermore, clinical studies over a 1-year period have demonstrated that tiotropium has impressive and maintained effects on lung function, symptoms and health-related quality of life, and may also reduce exacerbations. In a recent large scale comparative study over 6 months, tiotropium has been shown to cause superior bronchodilation and symptomatic improvement when compared to twice daily salmeterol in COPD. The only significant reported adverse event is dry mouth, which is found in approximately 10%-15% of subjects, but this is reversible and rarely causes discontinuation of therapy. Based on these promising features, it is likely that tiotropium used alone or in combination with other bronchodilators will emerge as first-line maintenance treatment for patients with airway obstruction due to COPD.
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