Recommended Dilution for Intravenous Administration of Polymyxin B
For intravenous administration of polymyxin B, dissolve 500,000 units in 300 to 500 mL of 5% Dextrose Injection for continuous drip infusion. 1
Dosing Recommendations
Standard Dosing
- For adults and children with normal renal function, administer 15,000 to 25,000 units/kg body weight/day 1
- A loading dose of 2-2.5 mg/kg is recommended, followed by a maintenance dose of 1.5-3 mg/kg/day divided into 2 doses 2
- Infusions may be given every 12 hours, but the total daily dose must not exceed 25,000 units/kg/day 1
- A 4-hour infusion is suggested to optimize pharmacokinetic/pharmacodynamic properties 2
Special Populations
- For infants with normal kidney function, up to 40,000 units/kg/day may be administered without adverse effects 1
- For patients with renal impairment, reduce the dose from 15,000 units/kg downward 1
- For patients on continuous renal replacement therapy (CRRT), dosage adjustments are not necessary for polymyxin B 2, 3
Administration Considerations
Preparation
- Dissolve 500,000 polymyxin B units in 300 to 500 mL of 5% Dextrose Injection for continuous drip infusion 1
- In the interest of safety, solutions for parenteral use should be stored under refrigeration 1
- Any unused portions should be discarded after 72 hours 1
Monitoring
- Monitor renal function closely during polymyxin B therapy 3, 4
- Be vigilant for early signs of nephrotoxicity, including albuminuria, cellular casts, azotemia, and diminishing urine output 3
- Watch for neurological adverse events such as perioral paresthesia, dizziness, and numbness of extremities, which are common but typically resolve without treatment 5
Clinical Considerations
Pharmacokinetics
- Polymyxin B is predominantly eliminated by non-renal pathways (median urinary recovery of only 4.04%) 6
- Unlike colistin, polymyxin B clearance does not show any relationship with creatinine clearance (r² = 0.008) 6
- The volume of distribution is approximately 0.219 L/kg, and the half-life is around 5.44 hours 5
Advantages Over Colistin
- Polymyxin B may be associated with a lower incidence of renal failure compared to colistin 2, 3
- Polymyxin B is available for direct intravenous administration and not as an inactive prodrug (unlike colistin) 2
- Polymyxin B requires less dose adjustment than colistin in renal impairment 4
Cautions and Contraindications
- Avoid concurrent use of other nephrotoxic medications when possible 3
- Discontinue NSAIDs during polymyxin B treatment, as they can exacerbate kidney injury 3
- Avoid the combination of NSAIDs, diuretics, and ACE inhibitors/ARBs during polymyxin B treatment as this dramatically increases acute kidney injury risk 3