Flag-Colis Injection contains Colistimethate Sodium (1 Million IU), a potent antibiotic used primarily for the treatment of serious infections caused by multidrug-resistant Gram-negative bacteria, including Pseudomonas aeruginosa, Acinetobacter species, and Klebsiella pneumoniae. It belongs to the polymyxin class of antibiotics and works by disrupting the bacterial cell membrane, leading to cell death. Flag-Colis Injection is typically reserved for severe infections such as ventilator-associated pneumonia, bloodstream infections, urinary tract infections, and complicated intra-abdominal infections when other antibiotics are ineffective or contraindicated. The injection is administered intravenously under medical supervision, with dosage adjusted based on the severity of infection, renal function, and patient response. Due to its potential nephrotoxicity and neurotoxicity, careful monitoring of kidney function and neurological status is essential during treatment. Common side effects may include mild to moderate kidney impairment, dizziness, and allergic reactions. Flag-Colis Injection should be used with caution in patients with pre-existing renal conditions and is contraindicated in individuals with known hypersensitivity to polymyxins. Proper use of this antibiotic is critical to prevent the development of resistance and ensure optimal therapeutic outcomes in managing life-threatening infections.