Poly-Rx topical

Structurally and pharmacologically related to colistin.14 105 Commercially available polymyxin B sulfate is a mixture of the sulfate salts of polymyxins B1 and B2.14 100 101 102 103 104

Usually bactericidal in action.100 101 102 105 109 125 131

Acts like a cationic detergent and binds to and damages bacterial cytoplasmic membrane of susceptible bacteria causing alteration of the osmotic barrier and leakage of essential intracellular components.14 105 112 125 144

Spectrum of activity is similar to that of colistin.14 105 125 140

Active in vitro against many gram-negative aerobic bacteria, but inactive against gram-positive bacteria, anaerobic bacteria, fungi, and viruses.105 112 125 144

Active in vitro against most strains of Pseudomonas aeruginosa, including many multidrug-resistant strains105 107 108 112 115 122 125 129 130 131 140 141 144 (e.g., those that produce metallo-β-lactamase).108 126 130 Also active in vitro against many strains of Acinetobacter baumannii, including multidrug-resistant strains.105 115 122 125 140 141

Active in vitro against most Enterobacteriaceae, including most strains of Citrobacter,125 141 Escherichia coli,105 112 125 141 Klebsiella pneumoniae,105 125 140 141 Salmonella,105 112 125 141 and Shigella,105 112 125 141 and some strains of Enterobacter.105 125 141 Generally inactive against Proteus,105 112 125 140 141 Providencia,112 125 Morganella,125 and Serratia marcescens.105 112 125 140 141

Has some activity against Haemophilus influenzae,105 125 Bordetella pertussis,105 125 and Legionella pneumophila,105 125 but inactive against Moraxella catarrhalis,125 Neisseria,105 125 and Brucella.125

May be active against some strains of Stenotrophomonas maltophilia,125 140 141 but inactive against Burkholderia cepacia (formerly Ps. cepacia).105 125 140 141

Resistance to polymyxin B has been reported rarely in Ps. aeruginosa105 125 131 140 141 143 and A. baumannii.125 138 140 141

Two types of resistance to polymyxin B have been identified in Ps. aeruginosa, including low-level, transmissible mutations and high-level, stepwise resistance.140

Complete cross-resistance occurs between polymyxin B and colistin; cross-resistance with other anti-infectives not reported to date.105 125 131 140 144