One of the most feared complications associated with chronic obstructive pulmonary disease (COPD) is acute exacerbation (AECOPD). On average, each COPD patient experiences 0.5 to 3.5 acute exacerbations per year, which is an important reason for the hospitalization, disease progression and mortality as well as decline in health status and lung function(1,2).
Treatment with a long-acting muscarinic antagonist (LAMA) reduces dyspnoea and the risk of exacerbations in patients with COPD by binding to muscarinic receptors in bronchial smooth musculature and thus inhibiting cholinergic bronchial constriction. LAMAs are given as inhalation therapy once daily (most often) or twice daily(3).
Most COPD-patients experience their worst symptoms and experience exacerbations in early morning hours, before getting out of bed(4). This might be explained by the physiological diurnal changes in the activity of the parasympathetic homeostasis system since this is most active at night to improve digestion and other secretions(5).
Correspondingly, the activity of the sympathetic system is physiologically suppressed at night, and stimulation of β-2 receptors is thus also low (and opposite for M-3 receptors). Taken together, the balance of sympathetic-parasympathetic tone is shifted significantly towards the latter. Most available LAMA treatments are dosed once daily in the morning.
Thus, for a COPD patient, being at a trough level of LAMA (which antagonizes the para-sympathetic system) at late night/early morning, may carry a hazard for the patient.
Studies have found that lung function measured as forced expiratory volume in 1 second (FEV1) improvement peaks approximately 2 hours after LAMA administration, and that FEV1 is still significantly improved at 7 hours post treatment but decreases towards the trough level of the LAMA(6). However, as a corollary to the above, when the medicine is probably most needed (02.00 a.m. to 07.00 a.m.), the effect is at its lowest level, which may not be desirable, since a low effect of the most important preventive medicine against AECOPD at this time, may lead to more exacerbations.
Evening administration, on the contrary, would lead to a greater and more certain effect regarding bronchodilation and reduced secretion in the early morning hours, and a maximum effect should be expected during the entire night.
