Can polymyxin B be infused in 100ml Normal Saline (NS)?

Polymyxin B Administration in Normal Saline

Yes, polymyxin B can be infused in 100ml Normal Saline (NS). 1

Administration Considerations

• Polymyxin B is administered intravenously and is not a prodrug (unlike colistin methanesulfonate which is an inactive prodrug) 2, 1
• The recommended administration is via intravenous infusion, with 100ml NS being an appropriate diluent volume 1
• A loading dose of 2-2.5 mg/kg is recommended for all patients, including those with renal dysfunction, followed by maintenance dosing of 1.5-3 mg/kg/day divided into two doses 2, 1
• Dosing should be based on total body weight rather than adjusted for renal function 1

Dosing Recommendations

• For directed therapy against carbapenem-resistant organisms, polymyxin B is dosed at 1.5-3 mg/kg/day with a loading dose of 2-2.5 mg/kg 2
• For patients on continuous renal replacement therapy, dose adjustment is not necessary, which is an advantage over colistin 2, 3
• The incidence of renal failure appears to be lower with polymyxin B than with colistin 2, 4

Important Dosing Conversions

• Polymyxin B sulfate: 1 mg = 10,000 units 2, 1
• For comparison with colistin: 1 million international units (IU) of colistin = 80 mg colistin methanesulfonate (CMS) = 33 mg colistin base activity (CBA) 2, 1

Monitoring and Safety Considerations

• Monitor renal function during treatment, as nephrotoxicity occurs in approximately 14% of patients with normal baseline renal function 1, 5
• Avoid concurrent use of other nephrotoxic drugs, such as vancomycin, which increases the risk of nephrotoxicity (HR = 1.89) 1, 5
• Contrast media use is also associated with increased nephrotoxicity risk (HR = 1.79) 5
• Higher daily doses by actual body weight are associated with increased nephrotoxicity risk (HR = 1.73) 5

Combination Therapy

• Polymyxin B combination therapy is strongly recommended over monotherapy for treating carbapenem-resistant gram-negative infections 2, 1
• For carbapenem-resistant Acinetobacter baumannii infections, if meropenem MIC is ≤32 mg/L, consider polymyxin B-carbapenem combination with extended-infusion of meropenem for 3 hours 2, 1

Infusion-Related Considerations

• Severe infusion-related adverse events are rare, with an incidence of only 0.9% even with high-dose polymyxin B regimens 6
• Less frequent dosing (once daily versus every 6 hours) may be associated with lower kidney tissue drug concentrations and potentially reduced nephrotoxicity 7