Polymyxin B is a broad-spectrum antibiotic that inhibits a variety of bacteria including Pseudomonas aeruginosa, Escherichia coli, Klebsiella and Haemophilus. It is also sensitive to strains that are resistant to other antibiotics. It is mostly used clinically as a sulfate preparation, mainly for infectious diseases and prevention of infections. Since this drug is not easily absorbed orally, it is usually administered intramuscularly or by intravenous infusion, or intrathecally, for the treatment of meningitis caused by Pseudomonas aeruginosa infection. This drug is slowly metabolized through the kidneys and has poor tissue diffusion, which can lead to some nephrotoxicity and slight tubular damage; therefore, it should be used with caution in patients with abnormal renal function or underlying renal disease.