Efficacy and safety of an intravenous amikacin-containing regimen as initial therapy in Mycobacterium avium complex pulmonary disease

Introduction The global incidence of Mycobacterium avium complex pulmonary disease (MAC-PD) has been increasing, particularly in Japan. Although current guidelines recommend adding intravenous amikacin (AMK-IV) for cavitary or severe disease, evidence supporting its use as initial therapy remains limited, especially among elderly patients. Methods This retrospective study included patients with cavitary MAC-PD who received an AMK-IV-containing regimen as initial therapy at Kurashiki Central Hospital between September 2021 and July 2024. AMK-IV dosing was adjusted based on therapeutic drug monitoring (TDM). The primary outcome was sputum culture conversion. Secondary outcomes included radiologic improvement, adverse events, recurrence, and all-cause mortality. Clinical characteristics and outcomes were compared between patients aged ≥75 and < 75 years. Results Twenty-one patients were analyzed (aged ≥75 years, n = 11; aged <75 years, n = 10; median age, 75 years; 76.2% female). TDM-guided dose adjustment of AMK-IV was performed in all patients, and outpatient treatment was continued using the adjusted dose. Target peak concentrations were achieved in 57.1% of patients, while target trough concentrations were achieved in all patients. At 6/12 months, sputum culture conversion was achieved in 56.3%/62.5% and radiologic improvement was observed in 83.3%/88.9%. No significant differences in sputum culture conversion or radiologic improvement were found between age groups. Treatment discontinuation occurred in two patients (9.5%), whereas 90.9% of elderly patients completed ≥3 months of AMK-IV. Conclusion AMK-IV added to a standard regimen for cavitary MAC-PD may be effective and safe. In this TDM-guided protocol, favorable outcomes were observed despite lower peak concentrations than those generally recommended.