Polymyxin B

INDICATIONS AND USAGE Acute Infections Caused by Susceptible Strains of Pseudomonas aeruginosa. Polymyxin B sulfate is a drug of choice in the treatment of infections of the urinary tract, meninges, and bloodstream caused by susceptible strains of Ps. aeruginosa . It may also be used topically and subconjunctivally in the treatment of infections of the eye caused by susceptible strains of Ps. aeruginosa . It may be indicated in serious infections caused by susceptible strains of the following organisms, when less potentially toxic drugs are ineffective or contraindicated: H influenzae , specifically meningeal infections. Escherichia coli , specifically urinary tract infections. Aerobacter aerogenes , specifically bacteremia. Klebsiella pneumoniae , specifically bacteremia. NOTE: IN MENINGEAL INFECTIONS, POLYMYXIN B SULFATE SHOULD BE ADMINISTERED ONLY BY THE INTRATHECAL ROUTE. To reduce the development of drug-resistant bacteria and maintain the effectiveness of polymyxin B and other antibacterial drugs, polymyxin B should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria. When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy.

WARNINGS Clostridium difficile associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including Polymyxin B for Injection, and may range in severity from mild diarrhea to fatal colitis. Treatment with antibacterial agents alters the normal flora of the colon leading to overgrowth of C. difficile . C. difficile produces toxins A and B which contribute to the development of CDAD. Hypertoxin producing strains of C. difficile cause increased morbidity and mortality, as these infections can be refractory to antimicrobial therapy and may require colectomy. CDAD must be considered in all patients who present with diarrhea following antibiotic use. Careful medical history is necessary since CDAD has been reported to occur over two months after the administration of antibacterial agents. If CDAD is suspected or confirmed, ongoing antibiotic use not directed against C. difficile may need to be discontinued. Appropriate fluid and electrolyte management, protein supplementation, antibiotic treatment of C. difficile , and surgical evaluation should be instituted as clinically indicated. Electrolyte and Acid/Base Abnormalities Postmarketing cases of renal tubulopathy (i.e., Pseudo-Bartter syndrome) have been identified with the use of intravenous polymyxins, including polymyxin B (see ADVERSE REACTIONS ). All cases reported hypokalemia and metabolic alkalosis. Other common findings included hypocalcemia, hypomagnesemia, increased potassium in the urine, normal serum creatinine, and normal blood pressure. Consider electrolyte monitoring during treatment. Normalization of electrolyte abnormalities may require drug discontinuation.