Recommended Colistin Dosing for Urinary Tract Infections
For the treatment of urinary tract infections (UTIs) caused by multidrug-resistant organisms, a loading dose of 9 MU (5 mg/kg) of colistin followed by a maintenance dose of 4.5 MU twice daily is recommended. 1
Standard Adult Dosing Regimen
- Loading dose: 9 MU (5 mg/kg) of colistin 2, 1
- Maintenance dose: 4.5 MU (2.5 mg × [(1.5 × CrCl) + 30]) twice daily, where CrCl represents creatinine clearance in mL/min 2, 1
- For patients with normal renal function, the daily dose ranges from 2.5 to 5 mg/kg per day of colistin base activity divided into 2 to 4 doses 3
- In obese individuals, dosage should be based on ideal body weight 3
Dose Adjustment for Renal Impairment
- Mild renal impairment (CrCl 50-79 mL/min): 2.5 to 3.8 mg/kg/day divided into 2 doses 3
- Moderate renal impairment (CrCl 30-49 mL/min): 2.5 mg/kg once daily or divided into 2 doses 3
- Severe renal impairment (CrCl 10-29 mL/min): 1.5 mg/kg every 36 hours 3
Administration Methods
- Direct intermittent administration: Slowly inject one-half of the total daily dose over 3-5 minutes every 12 hours 3
- Continuous infusion: Inject half the daily dose over 3-5 minutes, then administer the remaining half by slow IV infusion over the next 22-23 hours 3
Pediatric Dosing
- Loading dose: 0.15 MU/kg of colistin 1
- Maintenance dose: 0.075 MU/kg every 12 hours (equivalent to 2.5–5 mg colistin base activity per kg per day) 1
Monitoring and Safety Considerations
- Renal function should be closely monitored during colistin therapy due to risk of nephrotoxicity 2, 1
- Hypoalbuminemia and concomitant use of NSAIDs significantly increase the risk of nephrotoxicity 4
- Nephrotoxicity occurs in approximately 30% of patients but is generally reversible with 90% recovery of renal function after one month 4
Alternative Treatment Options for MDR UTIs
- For carbapenem-resistant Enterobacterales (CRE) causing UTIs:
Clinical Efficacy
- Clinical cure rates of 76.9% have been reported for colistin in treating nosocomial infections, including UTIs, caused by multidrug-resistant organisms 5
- For lower UTIs specifically, clinical cure rates of 89.5% have been reported even when optimal plasma concentrations are not achieved, suggesting that high urinary concentrations of colistin may be effective 6
Important Considerations and Pitfalls
- Colistin concentrations in urine can be much higher than in plasma, which may explain efficacy in UTIs even with suboptimal plasma levels 6
- Lower doses may be effective for lower UTIs caused by organisms with low MICs, potentially reducing nephrotoxicity 6
- For complicated UTIs with concurrent bacteremia, combination therapy may be more effective than monotherapy 7
- Colistin should be considered primarily for multidrug-resistant organisms with limited treatment options 8