Purpose: Rescue medication use is common in chronic obstructive pulmonary disease (COPD) patients and tends to increase with symptoms and disease severity. An analysis of baseline rescue medication use was conducted to inform on patient phenotypes and subsequent effects on lung function, symptoms, and safety following 12 weeks of nebulized glycopyrrolate (GLY) 25 µg twice daily or placebo in patients with moderate-tovery-severe COPD. Patients and Methods: Pooled data from the 12-week, placebo-controlled GOLDEN 3 and 4 studies (n=781) were used to assign patients into quarters based on baseline rescue medication use (ie, average puffs-per-day) during the run-in period. Placebo-adjusted trough forced expiratory volume in 1 second (FEV 1), St. George's Respiratory Questionnaire (SGRQ) total score and EXAcerbations of COPD Tool-Respiratory Symptoms (EXACT-RS) total score data were reported; safety was evaluated by reviewing the incidence of adverse events (AEs) and serious AEs (SAEs). Results: Baseline rescue medication use was a proxy for disease severity, evidenced by decreased lung function, increased health status scores, symptom scores and use of background long-acting β2-agonists and inhaled corticosteroids across quarters and treatment groups. Treatment with GLY led to greater improvements from baseline in trough FEV 1 , SGRQ and EXACT-RS scores compared with placebo in all rescue medication use quarters. Additionally, the SGRQ and EXACT-RS exhibited greater improvement with increased baseline rescue medication use with GLY treatment. In the Q4 patients, SGRQ (≥4-unit reduction) or EXACT-RS (≥2-unit reduction) responders were significantly greater with GLY compared with placebo. AE and SAE incidences were similar across quartiles. Conclusion: These results suggest that baseline rescue medication use assessments may be useful in the management of COPD. Treatment with nebulized GLY improved lung function and symptom scores, regardless of baseline rescue medication use. These results support the use of nebulized GLY for the treatment of COPD, independent of baseline rescue medication use.