polymyxin B + tigecycline

Polymyxin B + tigecycline is a combination of two antibiotics used primarily as a last-resort treatment for infections caused by multidrug-resistant Gram-negative bacteria, especially carbapenem-resistant Enterobacteriaceae (CRE) such as Klebsiella pneumoniae. Polymyxin B is a cationic polypeptide antibiotic that disrupts the bacterial cell membrane, leading to cell death. Tigecycline is a glycylcycline antibiotic that inhibits protein synthesis by binding to the 30S ribosomal subunit. The combination has been studied for its synergistic effects against bacteria resistant or heteroresistant to either agent alone, with evidence suggesting improved bactericidal activity in vitro and potential clinical benefit in severe infections where other options are limited[2][3][4]. However, both drugs carry significant risks—polymyxin B can cause nephrotoxicity and neurotoxicity, while tigecycline has been associated with increased mortality in some patient populations.