Colistin Dosing in Hemodialysis: Supplemental Dosing IS Required
No, this regimen is incomplete—patients on intermittent hemodialysis require a supplemental dose after each dialysis session in addition to the 9 million IU loading dose and 2 million IU every 12 hours maintenance dosing.
The Critical Issue with Your Proposed Regimen
The dosing you've described (9 MU load, then 2 MU q12h) addresses only the baseline maintenance needs but ignores the substantial drug removal that occurs during hemodialysis sessions. This is a common and dangerous pitfall.
Evidence-Based Dosing Framework
Loading Dose: Correct
- 9 million units (MU) of CMS is appropriate as the initial loading dose 1
- This loading dose is independent of renal function and should be given to all patients, including those on dialysis 2
Maintenance Dosing: Partially Correct But Incomplete
For patients on intermittent hemodialysis, you need TWO components:
Baseline maintenance dose: 2 million IU every 12 hours is reasonable for patients with severe renal impairment (CrCl 10-29 mL/min) per FDA labeling 3, though some patients on dialysis may require even less frequent dosing (1.5 mg/kg every 36 hours for the most severe impairment)
Supplemental post-dialysis dose: This is the missing piece in your regimen
Why Supplemental Dosing Matters
Recent pharmacokinetic evidence demonstrates that extracorporeal clearance during dialysis can account for up to 67% of total drug clearance 4. Without replacement dosing after dialysis, patients experience subtherapeutic colistin concentrations that:
- Fail to achieve the pharmacodynamic target (fAUC/MIC ≥12)
- Increase risk of treatment failure
- Potentially promote resistance development
The fundamental principle is clear: a loading dose establishes therapeutic levels, maintenance doses sustain them between dialysis sessions, and supplemental doses replace what dialysis removes 5.
Practical Dosing Algorithm for Intermittent HD
- Day 1: Give 9 MU loading dose
- Maintenance: 2 MU every 12 hours on non-dialysis days
- Dialysis days: Give supplemental dose immediately after each dialysis session 6
- The exact supplemental dose should be guided by the degree of dialytic clearance
- Research suggests supplemental dosing achieves >80% target attainment in RRT patients 6
Key Caveats
- Monitor renal function closely even in dialysis patients, as colistin nephrotoxicity remains a concern 1
- Standard dosing regimens frequently fail to achieve pharmacodynamic targets in dialysis patients 4
- The pharmacokinetics are highly variable in this population, influenced by dialysis modality, membrane type, and individual patient factors 4
- Consider therapeutic drug monitoring if available, targeting average steady-state concentrations of 2 mg/L 6
The Bottom Line
Your proposed regimen of 9 MU loading followed by 2 MU q12h addresses only part of the dosing equation. The supplemental post-dialysis dose is not optional—it's essential to maintain therapeutic drug levels and optimize clinical outcomes 5, 6. Omitting this component places your patient at risk for treatment failure due to subtherapeutic drug exposure during and after dialysis sessions.