Polymyxin B Reconstitution for IV Injection
Dissolve 500,000 polymyxin B units in 300 to 500 mL of 5% Dextrose Injection for continuous IV drip. 1
Reconstitution Protocol
The FDA-approved reconstitution method is straightforward:
- Take one vial containing 500,000 polymyxin B units
- Add to 300-500 mL of 5% Dextrose Injection
- Use for continuous drip infusion 1
Alternative Reconstitution for IM Use (Not Recommended)
While the FDA label describes dissolving 500,000 units in 2 mL of Sterile Water for Injection, 0.9% Sodium Chloride, or Procaine Hydrochloride 1% for intramuscular use, IM administration is not routinely recommended due to severe pain at injection sites, particularly in infants and children. 1
Dosing After Reconstitution
Once properly reconstituted for IV use:
- Adults and children with normal renal function: 15,000 to 25,000 units/kg/day
- Maximum daily dose: Must not exceed 25,000 units/kg/day
- Infusion frequency: Every 12 hours 1
- Infants: May receive up to 40,000 units/kg/day without adverse effects 1
Critical Dosing Adjustment
Reduce the dose from 15,000 units/kg downward in patients with renal impairment. 1 Creatinine clearance is a key covariate influencing drug exposure and should guide individualized dosing. 2
Storage Requirements
Critical storage guidelines to prevent loss of potency:
- Before reconstitution: Store at 20-25°C (68-77°F), protected from light 1
- After reconstitution: Must be refrigerated at 2-8°C (36-46°F) 1
- Discard unused portions after 72 hours 1
Research confirms that polymyxin B in 0.9% sodium chloride retains >90% potency for at least 24 hours at both room temperature and refrigeration, though stability does not extend reliably beyond 2 days. 3
Important Conversion Factor
Polymyxin B sulfate: 1 mg = 10,000 units 4
This conversion is essential when interpreting dosing recommendations expressed in different units across various guidelines and studies.
Common Pitfalls to Avoid
- Do not use 0.9% sodium chloride as the primary diluent for IV infusion—the FDA label specifically indicates 5% Dextrose Injection 1
- Do not store reconstituted solutions at room temperature beyond immediate use—refrigeration is mandatory 1
- Do not exceed 72-hour storage even under refrigeration 1
- Avoid combining with other nephrotoxic or ototoxic drugs when possible 4