Abstract
Background: The combination therapy for acute bronchitis with several plant extracts, such as Ivy and Thyme or Primrose and Thyme, is assumed to offer added benefit over single extract preparations. However, no clinical trials have yet demonstrated such a therapeutic advantage. Methods: In this three-arm, open-label, randomized clinical trial, patients with acute bronchitis were assigned to groups receiving Ivy extract EA 575 (Prospan(®) Cough Drops), Ivy/Thyme extract combination (Bronchipret(®) Drops), or Thyme/Primrose extract combination (Bronchicum(®) Drops) according to their respective labels. The primary endpoint was the assessment of non-inferiority, and the second endpoint was the assessment of superiority of Ivy vs. each of the two comparators (Ivy/Thyme and Thyme/Primrose) regarding the change in Bronchitis Severity Score between baseline and day 7. In total, 325 adult patients were considered for evaluation. Results: Non-inferiority of Ivy extract was statistically significant against both comparators (both p < 0.0001). Superiority of Ivy extract was statistically significant against Ivy/Thyme extract (p < 0.0001) but missed statistical significance against Thyme/Primrose extract (p < 0.0607). The incidence of adverse events was low and comparable between the groups. All adverse events were non-serious. Conclusions: these data revealed that Ivy extract EA 575 is non-inferior in acute bronchitis treatment compared to both comparators and superior to Ivy/Thyme.