At what Glomerular Filtration Rate (GFR) is Pyridium (Phenazopyridine) okay to give?

Pyridium (Phenazopyridine) Use Based on GFR

Pyridium should be avoided in patients with GFR <30 mL/min/1.73 m² due to increased risk of toxicity and acute kidney injury. 1, 2

Safety Considerations by GFR Level

• GFR ≥50 mL/min/1.73 m²: Standard dosing of Pyridium is generally acceptable 3
• GFR 30-50 mL/min/1.73 m²: Use with caution; consider reduced dosing and shorter duration of treatment 2
• GFR <30 mL/min/1.73 m²: Avoid use due to increased risk of acute tubular necrosis, acute interstitial nephritis, and methemoglobinemia 1
• Dialysis patients: Contraindicated due to inability to clear the medication effectively 1

Mechanism of Renal Toxicity

• Phenazopyridine can cause direct injury to renal tubular epithelial cells 2
• May induce pigment-induced nephropathy from associated hemolytic anemia 2
• Can cause acute interstitial nephritis even at therapeutic doses 2
• Methemoglobinemia from phenazopyridine can lead to hypoxic renal injury 1

Monitoring Recommendations

• For patients with borderline renal function (GFR 30-50 mL/min/1.73 m²) who require Pyridium:
  • Limit duration of therapy to shortest period possible (preferably <2 days) 2
  • Monitor renal function during treatment 2
  • Watch for signs of toxicity: skin/scleral yellowing, darkening urine beyond expected orange color 1
  • Discontinue immediately if signs of renal deterioration occur 2

Special Considerations

• Even small overdoses (1,200 mg) have been reported to cause acute renal failure in patients without prior kidney disease 1
• Patients with HIV, diabetes, or other comorbidities may be at higher risk for nephrotoxicity even with therapeutic doses 1
• When using for diagnostic purposes (e.g., ureteral orifice identification), administer the evening before procedure rather than same day to minimize renal exposure while maintaining efficacy 3

Alternative Options for Patients with CKD

• For urinary tract pain in patients with GFR <30 mL/min/1.73 m², consider:
  • Appropriate antibiotics (dose-adjusted for renal function) if infection present 4
  • Non-nephrotoxic analgesics with appropriate renal dosing 4
  • Treating underlying causes rather than using symptomatic therapy 4