Stable COPD: Initiating and Optimizing Therapy

In light of the above discussion, a combination of a short-acting beta-agonist and a muscarinic antagonist is recommended in all patients with COPD, unless the patient is on a long-acting muscarinic antagonist (LAMA).^7,18 In the latter case, a short-acting beta agonist used as a rescue inhaler is the best option. In our patient, albuterol was the choice for his short-acting bronchodilator, as he was using the LAMA tiotropium.

Are short-acting bronchodilators enough? What do we use for maintenance therapy?

All patients with COPD who are category B or higher according to the modified GOLD staging system should be on a long-acting bronchodilator:^7,19 either a long-acting beta-agonist (LABA) or a LAMA. Long-acting bronchodilators work on the same receptors as their short-acting counterparts but have structural differences. Salmeterol is the prototype long-acting selective beta-2 agonist. It is structurally similar to albuterol but has an elongated side chain that allows it to bind firmly to the area of beta receptors and stimulate them repetitively, resulting in an extended-duration of action.²⁰ Tiotropium on the other hand is a quaternary ammonium of ipratropium that is a nonselective muscarinic antagonist.²¹ Compared to ipratropium, tiotropium dissociates more quickly from M2 receptors, which is responsible for the undesired anticholinergic effects, while at the same time it binds M1 and M3 receptors for a prolonged time, resulting in an extended duration of action.²¹ Revefenacin is a new lung-selective LAMA that is under development and has shown promise among those with moderate to very severe COPD. Results are only limited to phase 3 trials, and clinical studies are still underway.²²

The currently available LABAs include salmeterol, formoterol, arformoterol, olodaterol, and indacaterol. The last 2 have the advantage of once-daily dosing rather than twice daily.^23,24 LABAs have been shown to improve lung function, exacerbation rate, and quality of life in multiple clinical trials.^23,25 Vilanterol is another LABA that has a long duration of action and can be used once daily,²⁶ but is only available in a combination with umeclidinium, a LAMA. Several LAMAs are approved for use in COPD, including the prototype tiotropium, in addition to aclidinium, umeclidinium, and glycopyrronium. These have been shown in clinical trials to improve lung function, symptoms, and exacerbation rate.^27-30

Patients can be started on either a LAMA or LABA depending on the individual patient's needs and the agent's adverse effects.⁷ Both have comparable adverse effects and efficacy, as detailed below. Concerning adverse effects, there is conflicting data concerning an association of cardiovascular events with both classes of long-acting bronchodilators. While clinical trials failed to show an increased risk,^25,31,32 several retrospective studies showed an increased risk of emergency room visits and hospitalizations due to tachyarrhythmias, heart failure, myocardial infarction, and stroke upon initiation of long-acting bronchodilators.^33,34 There was no difference in risk for adverse cardiovascular events between LABA and LAMA in 1 Canadian study, and slightly more with LABA in a study using an American database.^33,34 Wang et al reported that the risk of cardiovascular adverse effects, defined as hospitalizations and emergency room visits from heart failure, arrythmia, stroke, or ischemia, was 1.5 times the baseline risk in the first 30 days of starting a LABA or LAMA.³⁵ The risk was subsequently the same as baseline or even lower after that period. Urinary retention is another possible complication of LAMA supported by evidence from meta-analyses and retrospective studies, but not clinical trials; the possibility of urinary retention should be discussed with patients upon initiation.^36,37 Concerns about increased mortality with the soft mist formulation of tiotropium were put to rest by the Tiotropium Safety and Performance in Respimat (TIOSPIR) trial, which showed no increased mortality compared to Handihaler.³⁸

As far as efficacy and benefits, tiotropium and salmeterol were compared head-to-head in a clinical trial, and tiotropium increased the time before developing first exacerbation and decreased the overall rate of exacerbations.³⁹ No difference in hospitalization rate or mortality was noted in 1 meta-analysis, although tiotropium was more effective in reducing exacerbations.⁴⁰ The choice of agent should be made based on patient comorbidities and side effects. For example, an elderly patient with severe benign prostatic hyperplasia and urinary retention should try a LABA, while a LAMA would be a better first agent for a patient with severe tachycardia induced by albuterol.