Pyridium (Phenazopyridine) Dosing
The standard adult dose of Pyridium (phenazopyridine) is 200 mg orally three times daily after meals for symptomatic relief of urinary tract discomfort, with treatment limited to 2 days when used alongside antibiotics. 1
Standard Dosing Regimen
- Adults: 200 mg orally three times daily (total daily dose: 600 mg) 1
- The medication should be taken after meals to minimize gastrointestinal side effects 1
- Duration: Limit use to 2 days when combined with antibacterial therapy for urinary tract infections 1
Pediatric Dosing
- Children: 12 mg/kg/day divided into three doses 2
- Critical safety consideration: Even small ingestions can be toxic in children - as few as three 200-mg tablets (approximately 50 mg/kg) in a 2-year-old caused significant methemoglobinemia requiring methylene blue therapy 2
Dosing in Renal Impairment
Phenazopyridine is contraindicated in patients with impaired renal function and should not be used in this population. 3
- The drug and its metabolites are renally excreted and accumulate in renal insufficiency 3
- Acute renal failure has been reported even with single doses as low as 1,200 mg in patients without preexisting kidney disease 3
- Patients with preexisting renal disease are at particularly high risk for toxicity including acute tubular necrosis 3
Critical Safety Warnings
- Renal toxicity: Phenazopyridine can cause acute renal failure, even in patients with previously normal kidney function 3
- Methemoglobinemia: This is a dose-dependent complication that can occur even with therapeutic dosing in susceptible individuals 2
- Hematologic toxicity: Hemolytic anemia and myelosuppressive pancytopenia have been reported 4
- Yellow discoloration: The drug causes harmless orange-red discoloration of urine and may stain contact lenses 1
Clinical Monitoring
- Observe pediatric patients for 4-6 hours after ingestion or obtain methemoglobin levels, as even small doses can be toxic 2
- Discontinue immediately if skin or sclera develops yellow discoloration, which may indicate drug accumulation 3
- Monitor for signs of hemolysis or methemoglobinemia (cyanosis, shortness of breath) 3, 2
Common Pitfalls to Avoid
- Never prescribe in renal impairment: This is an absolute contraindication, not just a dose adjustment scenario 3
- Do not exceed 2 days of therapy: Phenazopyridine is purely symptomatic and prolonged use increases toxicity risk without additional benefit 1
- Do not use as monotherapy: This drug provides only symptomatic relief and must be combined with appropriate antibacterial therapy for urinary tract infections 1