Colistin Dose Conversion: 0.075 MU vs 75,000 IU
0.075 million units (MU) and 75,000 International Units (IU) are exactly the same dose—these are simply two different ways of expressing the identical amount of colistin. 1
Understanding the Conversion
- 1 million units = 1,000 IU 1
- Therefore, 0.075 MU × 1,000 = 75,000 IU 1
- Both expressions refer to the same quantity of colistin base activity 1
Critical Context for Pediatric Dosing with Renal Impairment
Since you're asking about pediatric patients with impaired renal function, here's what matters clinically:
Loading Dose (Always Full Dose Regardless of Renal Function)
- Always administer the full loading dose of 0.15 MU/kg (150,000 IU/kg) regardless of renal impairment 2
- Never reduce the loading dose in renal dysfunction—this is a critical error that leads to delayed therapeutic levels 2
Maintenance Dose Adjustments Based on Creatinine Clearance
For pediatric patients, adjust only the maintenance doses based on renal function 2:
- Normal renal function (CrCl ≥80 mL/min): 0.075 MU/kg (75,000 IU/kg) every 12 hours 2
- Moderate impairment (CrCl 30-49 mL/min): 2.5 mg CBA/kg once daily 2
- Severe impairment (CrCl 10-29 mL/min): 1.5 mg CBA/kg every 36 hours 2
Conversion Between Units
The FDA label states that each 150 mg vial reconstituted provides 75 mg/mL colistin base activity 3. The relationship between different colistin units can cause dosing errors, so always verify which unit system your institution uses 1.
Mandatory Monitoring
- Monitor renal function 2-3 times per week during therapy 2, 4
- Nephrotoxicity occurs in 5.8% of pediatric patients 2, 5
- Do not underdose to prevent nephrotoxicity—subtherapeutic levels cause treatment failure while still carrying nephrotoxic risk 2, 4
Critical Pitfall to Avoid
Never use colistin as monotherapy for serious infections—always combine with at least one additional active agent 2, 5