Efficacy and safety of inhaled ambroxol hydrochloride solution in Chinese pediatric patients with acute lower respiratory tract infections: a real-world, multicenter, open-label, single-arm study.

Background: Although randomized controlled trials (RCTs) have confirmed the mucolytic efficacy of ambroxol hydrochloride solution for inhalation (AHSI) in selected cohorts, their stringent exclusion criteria often omit children with comorbidities and complex presentations encountered in routine practice. Consequently, real-world evidence is needed to evaluate the effectiveness and safety of AHSI in a broader, clinically representative pediatric population with acute lower respiratory tract infections (ALRTIs). This study therefore aimed to assess the real-world effectiveness, safety, and nebulizer compatibility of a 7-day AHSI regimen added to standard care in a large, multicenter cohort of hospitalized pediatric patients with ALRTI. Methods: This real-world, multicenter, open-label, single-arm study enrolled hospitalized patients aged ≥6 months with ALRTI (acute bronchitis, bronchiolitis, or pneumonia) and symptom duration <7 days across 62 centers in China (April 2021-April 2022). Key inclusion criteria included a cough score ≥2 (0-4 scale), tenacious sputum, and difficulty expectorating. Major exclusions comprised severe pneumonia, bronchial asthma, interstitial lung disease, significant hepatic or renal dysfunction [alanine aminotransferase (ALT) >1.5× upper limit of normal (ULN), total bilirubin (TBil) or serum creatinine (Scr) > ULN], other severe comorbidities, known hypersensitivity to ambroxol, or recent trial participation. Participants received weight-based doses of nebulized AHSI twice daily for 7 days as add-on to standard care. Follow-up visits occurred at day 4 and day 7 (end of treatment). Primary endpoints were the cough improvement rate (defined by a reduction in cough score) and the overall clinical response rate (investigator-assessed improvement). Secondary endpoints included changes from baseline in cough, throat rales, and pulmonary auscultation scores. Safety assessments comprised monitoring of adverse events (AEs) (coded with MedDRA), vital signs, and laboratory tests (hematology, biochemistry, urinalysis) at baseline and day 7. Results: A total of 2,599 children were enrolled [full analysis set (FAS)]. At baseline, mean age was 3.60±2.50 years, 57.6% were male, and symptom scores were: cough 2.10±0.30, throat sputum 1.65±0.59, lung auscultation 1.44±0.70. In the FAS, the cough improvement rate was 96.73% [95% confidence interval (CI): 96.05-97.41] and the clinical response rate was 94.73% (95% CI: 93.87-95.59). All symptom scores decreased significantly from baseline to day 7 (P<0.001). Drug-related AEs (DRAEs) occurred in 0.39% of patients, predominantly mild-to-moderate rash, transient liver enzyme elevations, and gastrointestinal events; no serious DRAEs were reported. Outcomes were consistent across pneumonia and bronchitis subgroups and across various nebulizer types. Conclusions: This large real-world study demonstrated that a 7-day course of AHSI, added to standard care, was associated with clinically meaningful improvements in respiratory symptoms and a favorable safety profile in children with ALRTI. The consistent effects across disease subtypes and nebulizer devices underscore the practical utility of AHSI in diverse pediatric settings. While the single-arm design limits causal inference, these findings provide robust real-world evidence supporting AHSI as an effective expectorant option. Prospective confirmation through RCTs will further define its role in first-line therapy.