Colistin and Polymyxin B
TREATMENT
Colistimethate sodium (colistin; 300 mg IV ? 1, then 180 mg IV q12h) and polymyxin B (15,000-25,000 units/kg/d IV divided q12h) are bactericidal polypeptide antibiotics that kill gram-negative bacteria by disrupting the cell membrane.
These drugs are typically active against CRE and P. aeruginosa, but have recently been replaced by newer, safer β-lactam antibiotics (outlined above). Notably, these agents are inactive against Proteus, Providencia, Burkholderia, and Serratia.SPECIAL CONSIDERATIONS
• These medications should only be given under the guidance of an experienced clinician and as last-line agents due to significant nephrotoxicity (~30%) and CNS toxicity (~10%). Inhaled colistin (75-150 mg q12h via nebulizer) is better tolerated than the IV formulation, generally causing only mild upper airway irritation, and has some effectiveness as adjunctive therapy for MDR P. aeruginosa or
Acinetobacter pulmonary infections.
• Adverse events with parenteral therapy include paresthesias, slurred speech, peripheral numbness, tingling, and significant dose-dependent nephrotoxicity. The dosage should be carefully reduced in patients with renal insufficiency because overdosage can result in neuromuscular blockade and apnea. Serum creatinine should be monitored daily early in therapy and then at a regular interval for the duration of therapy. Concomitant use with aminoglycosides, other known nephrotoxins, or neuromuscular blockers should be avoided.