Colistin is an antibiotic that belongs to the polymyxin class. It is primarily used to treat infections caused by multidrug-resistant bacteria, particularly Gram-negative organisms. Colistin works by disrupting the bacterial cell membrane, leading to cell death. Due to its potential for toxicity, especially to the kidneys, colistin is often reserved for severe infections when other antibiotics are ineffective. It is administered either intravenously or through inhalation for respiratory infections. The rise of antibiotic resistance has made colistin an important option in modern medicine, despite its side effects.