Cephalexin Dosing for UTI in End-Stage Renal Disease on Hemodialysis
For an adult with end-stage renal disease on intermittent hemodialysis who has an uncomplicated lower urinary tract infection, administer cephalexin 250-500 mg orally three times weekly, immediately after each dialysis session. 1
Dosing Strategy
Recommended Regimen
- Dose: 250-500 mg orally per dialysis session 1
- Frequency: Three times weekly, matching the typical hemodialysis schedule 1
- Timing: Immediately after dialysis completion to prevent premature drug removal 1, 2
Rationale for Post-Dialysis Administration
- Hemodialysis removes approximately 58% of cephalexin from serum over a 6-hour dialysis session 3
- Administering after dialysis ensures adequate therapeutic levels are maintained between sessions 2
- In anephric patients, single doses of 250-500 mg result in high, prolonged serum concentrations with peak levels typically within 1 hour 3
Pharmacokinetic Considerations in ESRD
Drug Clearance and Half-Life
- In patients with chronic renal failure, cephalexin's serum half-life extends from 1.1 hours (normal) to 6.1-18.1 hours 4
- Antimicrobial activity persists for 24 hours in renal failure patients, even after dialysis 4
- Despite reduced renal function, urinary concentrations remain adequate (500-1000 mcg/mL) for treating common uropathogens like E. coli, Klebsiella, and Proteus mirabilis 3, 5
Critical Dosing Principle
- Maintain standard individual doses while extending the dosing interval—never reduce the dose size 2
- Reducing individual doses leads to subtherapeutic peak concentrations and treatment failure 2
Alternative Considerations
When Cephalexin May Not Be Optimal
While cephalexin is appropriate for uncomplicated lower UTI, β-lactams including cephalexin are considered alternative rather than first-line agents due to inferior efficacy compared to other UTI antimicrobials 6
Preferred Alternatives in Hemodialysis Patients
- Levofloxacin 750 mg orally three times weekly (after dialysis) is recommended as a first-line option 2
- Ciprofloxacin 500 mg orally three times weekly (after dialysis) is also recommended, particularly for complicated UTIs 2
- Fluoroquinolones should be reserved for situations where resistance to first-line agents is documented or suspected to exceed 10% 6
Safety Profile
Advantages of Cephalexin in ESRD
- Minimal nephrotoxic potential compared to aminoglycosides, which cause nephrotoxicity in 4% of patients with 25% irreversibility 1
- Low incidence of side effects due to lack of intracellular penetration 5
- Low protein binding and no measurable metabolism in body fluids 5
Agents to Avoid
- Aminoglycosides (gentamicin, tobramycin) should not be used as first-line therapy due to substantial risk of irreversible ototoxicity in hemodialysis patients 2
Treatment Duration and Monitoring
Duration
- Standard 5-7 day courses are appropriate for uncomplicated UTI 7
- In hemodialysis patients receiving three-times-weekly dosing, this translates to 2 weeks of calendar time
Common Pitfall
The most critical error is administering cephalexin before dialysis or reducing individual dose sizes rather than extending intervals—both practices result in subtherapeutic levels and treatment failure 2