Inhaled muscarinic antagonists for COPD--does an anti-inflammatory mechanism really play a role?

The long acting inhaled muscarinic antagonist tiotropium (Spiriva) improves lung function in patients with COPD. In addition, tiotropium reduces exacerbation frequency, dyspnoea and improves exercise capacity. As the latter has been associated with airway inflammation then this suggests that, in addition to the well-known anti-bronchoconstrictor effect, tiotropium might also display anti-inflammatory properties. With our current state of knowledge, however, it is not necessary to postulate an anti-inflammatory effect for tiotropium (Spiriva), rather inhibition of smooth muscle constriction with subsequent effects on lung hyperinflation (and possibly pulmonary circulation) can explain the effects on exacerbation frequency, dyspnoea and exercise capacity. Recent reports suggest that tiotropium can inhibit viral activation of inflammation and vagal nerve stimulation, suggesting a mechanism by which tiotropium can inhibit viral induction of exacerbations in COPD.