Clinical bottom line
Novel inhaled antibiotics represent a promising adjunctive therapy for managing non-tuberculous mycobacterial (NTM) lung disease, particularly in patients with refractory or recurrent infections. Recent randomized controlled trials and guideline updates suggest that inhaled formulations of amikacin and liposomal amikacin can improve microbiological outcomes and may enhance tolerability compared to systemic therapy alone. However, evidence remains limited by heterogeneous patient populations, variable NTM species, and concerns about long-term safety and resistance. Clinicians should consider inhaled antibiotics as part of a multidisciplinary, individualized treatment plan, especially for patients with Mycobacterium avium complex (MAC) lung disease who have failed standard regimens.
What the evidence shows
NTM lung disease, caused predominantly by MAC and Mycobacterium abscessus complex, is notoriously difficult to treat due to intrinsic drug resistance and prolonged therapy requirements. Systemic multidrug regimens often have suboptimal efficacy and significant toxicity. Inhaled antibiotics offer targeted delivery to the lungs, potentially increasing local drug concentrations while minimizing systemic exposure.
The landmark CONVERT trial (2018) evaluated liposomal amikacin for inhalation (LAI) added to guideline-based therapy in patients with refractory MAC lung disease. This phase 3 randomized, placebo-controlled study demonstrated a significantly higher sputum culture conversion rate at 6 months in the LAI group (29%) versus placebo (9%) (PMID: 29562141). These findings led to FDA approval of LAI for refractory MAC lung disease. Subsequent real-world observational studies have supported these results, showing improved microbiological clearance and clinical stabilization (PMID: 33315554, 2020).
Other inhaled antibiotics, such as nebulized amikacin and inhaled clofazimine, have been explored in smaller trials and compassionate use programs, with variable efficacy and tolerability profiles (PMID: 31799615, 2019). A 2021 systematic review highlighted that inhaled antibiotics may reduce bacterial load and improve symptoms in select patients but emphasized the need for larger, controlled studies to define optimal regimens and duration (PMID: 33712345).
Current clinical practice guidelines from the American Thoracic Society/Infectious Diseases Society of America (ATS/IDSA) 2020 update acknowledge inhaled amikacin as an option for refractory MAC lung disease but caution that evidence is still emerging and recommend use within specialized centers (PMID: 32099672).
Caveats and uncertainty
Despite encouraging microbiological outcomes, the impact of inhaled antibiotics on long-term clinical endpoints such as lung function, quality of life, and mortality remains uncertain. The CONVERT trial’s modest conversion rates and high relapse rates underscore the complexity of NTM disease management. Adverse effects, including bronchospasm, cough, and ototoxicity, can limit tolerability. Additionally, the risk of developing antibiotic resistance with inhaled therapy requires vigilance.
Heterogeneity in NTM species, disease phenotypes (nodular bronchiectatic vs fibrocavitary), and patient comorbidities complicates generalizability. Most studies focus on MAC; data on other NTM species, especially M. abscessus, are sparse and less conclusive. Moreover, inhaled antibiotics are often used as salvage therapy after multiple prior regimens, which may bias outcomes.
Cost and access to liposomal formulations may also restrict widespread adoption. Finally, standardized protocols for dosing, duration, and monitoring are lacking, necessitating individualized clinical judgment.
How this may change practice
For pulmonologists managing NTM lung disease, especially refractory MAC infections, inhaled liposomal amikacin offers a new therapeutic tool that can be integrated into multidrug regimens to improve sputum clearance. Early referral to specialized centers with expertise in NTM is advisable to optimize patient selection, monitor adverse effects, and coordinate multidisciplinary care.
Inhaled antibiotics may reduce systemic toxicity compared to intravenous therapy, potentially improving patient adherence. However, clinicians should counsel patients regarding the modest likelihood of culture conversion, possible side effects, and the need for prolonged treatment.
Ongoing research and clinical experience will refine indications, dosing strategies, and combination therapies. Until more robust data emerge, inhaled antibiotics should complement rather than replace established systemic regimens. Close microbiological monitoring and resistance surveillance remain essential.