Despite current guidelines and the range of available treatments, over a half of patients with
asthma continue to suffer from poor symptomatic control and remain at risk of future worsening. Although a number of non-pharmacological measures are crucial for good clinical management of
asthma, new therapeutic controller medications will have a role in the future management of the disease. Several long-acting
anticholinergic bronchodilators are under investigation or are available for the treatment of
respiratory diseases, including
tiotropium bromide,
aclidinium bromide,
glycopyrronium bromide,
glycopyrrolate and
umeclidinium bromide, although none is yet licensed for the treatment of
asthma. A recent Phase III investigation demonstrated that the once-daily long-acting
anticholinergic bronchodilator tiotropium bromide improves lung function and reduces the risk of exacerbation in patients with symptomatic
asthma, despite the use of inhaled
corticosteroids (ICS) and long-acting β2-agonists (LABAs). This has prompted the question of what the rationale is for long-acting
anticholinergic bronchodilators in
asthma. Bronchial smooth muscle contraction is the primary cause of reversible airway narrowing in
asthma, and the baseline level of contraction is predominantly set by the level of '
cholinergic tone'. Patients with
asthma have increased bronchial smooth muscle tone and mucus hypersecretion, possibly as a result of elevated
cholinergic activity, which
anticholinergic compounds are known to reduce. Further,
anticholinergic compounds may also have anti-inflammatory properties. Thus, evidence suggests that long-acting
anticholinergic bronchodilators might offer benefits for the maintenance of
asthma control, such as in patients failing to gain control on ICS and a LABA, or those with frequent exacerbations.