Used primarily as an antibiotic to treat severe infections caused by multidrug-resistant Gram-negative bacteria, especially Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumoniae. Commonly administered in cases of respiratory tract infections, particularly in cystic fibrosis patients with chronic lung infections. Also used in urinary tract infections, blood infections, and wound or burn infections when other antibiotics are ineffective. Often reserved as a last-line treatment due to potential toxicity. Can be given intravenously, intramuscularly, or by inhalation, with inhalation route helping to deliver high concentrations directly to the lungs while minimizing systemic side effects.