Phenazopyridine Dosing
The recommended adult dose of phenazopyridine is 200 mg orally three times daily after meals, with treatment duration not exceeding 2 days when used with antibiotics for urinary tract infections. 1
Standard Adult Dosing
- 100 mg tablets: Two tablets (200 mg total) three times daily after meals 1
- 200 mg tablets: One tablet three times daily after meals 1
- Maximum duration: Do not exceed 2 days when used concomitantly with antibacterial agents 1
Critical Dosing Considerations in Renal Impairment
Phenazopyridine is contraindicated in patients with renal insufficiency (creatinine clearance <50 mL/min). 2
Key Safety Points:
- Absolute contraindication: Patients with creatinine clearance <50 mL/min should not receive phenazopyridine due to risk of acute renal failure 2
- Preexisting kidney disease: Even therapeutic doses can cause acute tubular necrosis, acute interstitial nephritis, or pigment-induced nephropathy in patients with compromised renal function 3, 4
- Dose-dependent toxicity: Acute renal failure has been reported with doses as low as 1,200 mg (single ingestion) in patients without prior kidney disease 3
Adolescent Dosing
- Adolescents: Use adult dosing (200 mg three times daily after meals) 1
- Renal screening required: Check creatinine clearance before prescribing, as acute renal failure can occur even in young patients without known kidney disease 3
Common Pitfalls to Avoid
- Do not extend treatment beyond 2 days: Prolonged use (e.g., 6 weeks at 200 mg four times daily) significantly increases nephrotoxicity risk 5
- Avoid contrast studies during treatment: Patients on phenazopyridine who develop renal dysfunction should not receive radiographic contrast media, as this causes additive nephrotoxicity 5
- Monitor for early toxicity: Watch for yellow skin discoloration, methemoglobinemia, or rising creatinine—these indicate drug accumulation and require immediate discontinuation 3, 4
Additional Contraindications
Phenazopyridine should not be used in patients with: 2
- Severe hepatitis or liver disease
- Glucose-6-phosphate dehydrogenase (G6PD) deficiency
- Previous hypersensitivity to phenazopyridine
- Pregnancy
Clinical Context
While phenazopyridine provides effective symptomatic relief (57.4% reduction in dysuria pain within 6 hours), 6 its narrow therapeutic window and nephrotoxic potential demand strict adherence to the 2-day maximum duration and mandatory renal function screening before initiation. 1, 2