Florastor (Saccharomyces boulardii) for UTI Treatment
Florastor (Saccharomyces boulardii) is not effective for treating urinary tract infections and should not be used as UTI therapy. 1
Why Florastor Does Not Treat UTIs
Saccharomyces boulardii is a probiotic yeast with documented benefits only for gastrointestinal diseases, specifically diarrhea prevention and treatment—it has no established antimicrobial activity against uropathogens. 1
The therapeutic mechanisms of S. boulardii involve anti-inflammatory and immunomodulatory effects on the intestinal mucosa, not urinary tract antimicrobial action. 1
While one small pilot study (n=32) showed D-mannose combined with S. boulardii reduced post-cystoscopy UTI incidence compared to no treatment (0% vs 18.8%, p=0.044), this was a prevention study in a highly specific procedural context, not treatment of established UTI. 2
What Actually Works for UTI in Patients with Renal Impairment
Antibiotic Selection Based on Renal Function
Calculate creatinine clearance using the Cockcroft-Gault equation before prescribing—serum creatinine alone is inadequate in elderly patients with chronic kidney disease. 3, 4
Ciprofloxacin and levofloxacin maintain adequate urine concentrations even as renal function declines, making them suitable options when local resistance is <10%. 5, 6
Avoid sulfamethoxazole and nitrofurantoin when creatinine clearance is <50 mL/min, as urine concentrations become inadequate for efficacy. 5
Fosfomycin, nitrofurantoin, or pivmecillinam show minimal age-associated resistance in elderly patients but require adequate renal function. 3
Dosing Adjustments for Fluoroquinolones in Renal Impairment
Levofloxacin 750 mg initially, then 750 mg every 48 hours for CrCl 20-49 mL/min. 4
Levofloxacin 500 mg initially, then 500 mg every 48 hours for CrCl 10-19 mL/min or <10 mL/min. 4
Standard dosing: Levofloxacin 500 mg once daily or ciprofloxacin 500 mg twice daily for 7-14 days in complicated UTI. 4, 6
Critical Considerations for Patients with Chronic Medical Conditions
All UTIs in men are considered complicated by definition and require longer treatment duration (7-14 days) compared to uncomplicated cystitis in women. 4
Patients with diabetes, immunosuppression, or indwelling catheters have higher rates of antimicrobial resistance and require culture-guided therapy. 4
Hydration with saline prior to nephrotoxic drug exposure provides the most consistent benefit in preventing further renal injury. 7
Monitor for drug interactions closely, as polypharmacy is common in patients with chronic kidney disease and increases risk of adverse effects. 3, 7
When NOT to Treat
Do not treat asymptomatic bacteriuria in patients with chronic kidney disease—strong evidence shows no benefit and high-quality evidence demonstrates harm including C. difficile infection and increased antimicrobial resistance. 8
Required symptoms for true UTI include new-onset dysuria, frequency, urgency, suprapubic pain, fever, or costovertebral angle tenderness—not just a positive urine culture. 3, 4
Common Pitfalls to Avoid
Do not use macrolides (including azithromycin) for UTI treatment, as they achieve inadequate urinary concentrations and lack activity against common uropathogens. 4
Do not rely on serum creatinine alone to assess renal function—elderly patients have reduced muscle mass that falsely normalizes creatinine despite significant renal impairment. 3, 4
Avoid fluoroquinolones in elderly patients when possible due to significantly increased risk of severe tendon disorders including tendon rupture. 4
Do not assume probiotics like Florastor substitute for appropriate antimicrobial therapy in established UTI. 1