Once-daily vilanterol-fluticasone versus twice-daily formoterol-fluticasone in chronic obstructive pulmonary diseases: Real-world evidence on dosing frequency, adherence, and clinical outcomes

Objectives: Chronic obstructive pulmonary disease (COPD) affects approximately 7.4% of Indians above 30 years. Long-acting beta-agonist/inhaled corticosteroid combinations are cornerstone therapy for symptomatic COPD. Poor medication adherence, a critical and modifiable determinant of therapeutic success, is substantially influenced by dosing frequency. The study aimed to compare treatment adherence patterns and associated clinical outcomes between once-daily vilanterol-fluticasone furoate (VI/FF) and twice-daily formoterol-fluticasone propionate (FOR/FP) in real-world COPD management, with a focus on dosing simplification as a pragmatic intervention. Materials and Methods: This prospective observational study enrolled 120 COPD patients (post-bronchodilator forced expiratory volume in 1 s (FEV1)/forced vital capacity <0.70) at a tertiary care center. Patients received VI/FF 25/100 mcg once daily ( n = 60) or FOR/FP 6/250 mcg twice daily ( n = 60) based on physician judgment and patient preference. Primary outcomes included FEV1 changes, exacerbation rates, and COPD assessment test (CAT) scores at 12 and 24 weeks. Adherence was assessed by dose counter review, prescription refill documentation, and structured patient interview. Propensity score matching and multivariable adjustment were employed to address confounding by indication. Results: At 24 weeks, treatment adherence was significantly superior with VI/FF (91.3% vs. 76.4%, p <0.001), driven primarily by once-daily convenience. This adherence advantage was associated with greater trough FEV1 improvement (mean difference 89 mL, 95% confidence interval [CI]: 52–126, p <0.001), superior CAT score reduction (mean difference −2.8 points, 95% CI: −4.5–−1.1, p = 0.002), and 42% fewer exacerbations (rate ratio 0.58, 95% CI: 0.38–0.88, p = 0.011). Mediation analysis suggested adherence accounted for approximately 31% of the exacerbation benefit. Both treatments showed comparable safety profiles. Conclusion: Once-daily VI/FF was associated with substantially superior treatment adherence compared to twice-daily FOR/FP, and this adherence advantage was associated with better clinical outcomes.