Polymyxin B1 Isoleucine is primarily used in the medical field as an antibiotic, particularly for treating infections caused by Gram-negative bacteria. It is effective against strains that are resistant to other antibiotics, making it a critical option in severe cases. The compound works by disrupting the bacterial cell membrane, leading to cell death. It is often administered intravenously or topically, depending on the infection site. In clinical settings, it is used to treat conditions like urinary tract infections, bloodstream infections, and wound infections. Additionally, it is sometimes included in combination therapies to enhance its efficacy or reduce the risk of resistance development. Due to its potency, it is typically reserved for cases where other treatments have failed or are unsuitable.