TMP-SMX Dosing for Dialysis Patients with Infection
For hemodialysis patients with infection, administer TMP-SMX at approximately 5-10 mg/kg of the trimethoprim component after each dialysis session (three times weekly), with higher doses (toward 10 mg/kg) reserved for serious infections. 1
Dosing Strategy by Infection Severity
Mild-to-Moderate Infections
- Administer one double-strength tablet equivalent (160 mg TMP/800 mg SMX) IV after each dialysis session, translating to approximately 5 mg/kg TMP component three times weekly 1
- This post-dialysis timing is critical—never dose before dialysis, as 44-64% of TMP and 57-84% of SMX are removed during a single dialysis session 2, 3
Serious Infections (e.g., Pneumocystis pneumonia, severe catheter-related bloodstream infections)
- Dose at 5-10 mg/kg TMP component after each dialysis session, with consideration of the higher end (toward 10 mg/kg) for life-threatening infections 1
- For PCP specifically, while non-dialysis patients receive 15-20 mg/kg/day divided every 6 hours 4, dialysis patients require dose modification due to substantial drug removal 2, 3
Critical Timing Considerations
Always administer TMP-SMX immediately after dialysis completion, not before or during the session 1:
- Dialyzer clearances are substantial: 38-94 ml/min for TMP and 42-51 ml/min for SMX 2, 3
- Pre-dialysis dosing wastes medication and leaves patients undertreated 1
- The elimination half-life during dialysis is only 6.0 hours for TMP and 3.1 hours for SMX 3
Common Pitfalls to Avoid
Do NOT Use Standard Renal Dosing Charts
- Standard CKD dosing recommendations (which suggest dose reduction for creatinine clearance <30 mL/min) do not apply to dialysis patients 1, 4
- The FDA label recommends "half the usual regimen" for CrCl 15-30 mL/min 4, but this guidance is for non-dialysis patients and will result in dangerous underdosing in dialysis patients 1, 2
Avoid Dose Reduction Based on Renal Impairment Alone
- Dialysis patients actually require supplementation after each session due to drug removal, not dose reduction 1
- Recent pharmacokinetic data demonstrate that current conservative dosing recommendations lead to subtherapeutic levels 2
Monitoring and Drug Interactions
Monitor closely for the following 1:
- Drug interactions with warfarin (increased anticoagulation effect)
- Drug interactions with antidiabetic agents (increased hypoglycemia risk)
- Hematologic toxicity: obtain CBC with differential at baseline and monthly 5
- Maintain adequate fluid intake in patients with residual urine output to minimize crystalluria risk 1
Evidence Quality Note
The dosing recommendation of 5-10 mg/kg TMP post-dialysis three times weekly represents a synthesis of multiple guideline sources 1 and is supported by pharmacokinetic studies demonstrating substantial dialytic removal 2, 3. A 2024 Japanese study found no mortality difference between high-dose and low-dose regimens in hemodialysis patients with PJP 6, though this study was underpowered. The 2013 pharmacokinetic study provides the strongest evidence that current conservative dosing leads to underdosing 2.