Introduction
Phenazopyridine hydrochloride is a urinary analgesic medication that provides local analgesia to the urinary tract mucosa. It is chemically classified as an azo dye and has been used clinically for decades to relieve symptoms associated with urinary tract irritation. Unlike antimicrobial agents used for urinary tract infections, phenazopyridine provides symptomatic relief without treating the underlying infection.
Mechanism of Action
Phenazopyridine exerts a direct topical analgesic effect on the urinary tract mucosa. The exact mechanism is not fully understood, but it is believed to interfere with sensory receptors in the urinary tract, reducing pain perception. As an azo compound, it is excreted renally where it achieves local analgesic effects. The drug does not possess antimicrobial properties and does not treat the underlying cause of urinary symptoms.
Indications
- Symptomatic relief of pain, burning, urgency, frequency, and other discomforts arising from irritation of the lower urinary tract mucosa
- Temporary symptomatic relief while awaiting definitive treatment for urinary tract infections
- Post-operative urinary tract instrumentation relief
- Diagnostic procedures involving the urinary tract
Dosage and Administration
Adults: 200 mg orally three times daily after meals Available formulations: 95 mg, 100 mg, and 200 mg tablets Special Populations:- Renal impairment: Contraindicated in significant renal impairment (GFR <50 mL/min)
- Hepatic impairment: Use with caution; limited data available
- Geriatric patients: Consider reduced dosing due to potential decreased renal function
- Pediatric patients: Safety and efficacy not established for children under 6 years
- Take with or after meals to minimize gastrointestinal upset
- Do not crush or chew tablets
- Typical treatment duration: 2 days when used with antibacterial therapy
Pharmacokinetics
Absorption: Rapidly absorbed from the gastrointestinal tract Distribution: Distributed throughout the body tissues; achieves high concentrations in the urinary tract Metabolism: Hepatic metabolism to unknown metabolites Elimination: Primarily renal excretion (65% within 24 hours); turns urine orange-red color Half-life: Approximately 3-4 hours Onset of action: Within 30 minutes to 1 hour Duration of effect: 4-6 hoursContraindications
- Hypersensitivity to phenazopyridine or any component of the formulation
- Significant renal impairment (glomerular filtration rate <50 mL/min)
- Hepatic insufficiency
- Glomerulonephritis
- Severe hepatitis
- Pyelonephritis during pregnancy
- Children under 6 years of age
Warnings and Precautions
Boxed Warning: None Important precautions:- May cause hemolytic anemia in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency
- Can cause methemoglobinemia, particularly at higher doses or in susceptible individuals
- May interfere with laboratory tests based on color reactions (urine glucose, ketones, bilirubin, etc.)
- Discontinue use if skin or sclera develop yellowish discoloration (may indicate accumulation)
- Use beyond 2 days may mask underlying conditions requiring treatment
- Not for long-term use due to risk of accumulation and toxicity
Drug Interactions
Clinically significant interactions:- Sulfonamides: May increase risk of crystalluria
- Other oxidizing drugs: Increased risk of methemoglobinemia
- Urinary alkalizing agents: May reduce efficacy due to decreased urinary concentration
- Laboratory test interference: Alters results of urine tests based on colorimetric methods
Adverse Effects
Common (≥1%):- Headache (5-10%)
- Gastrointestinal distress (nausea, vomiting, diarrhea) (3-8%)
- Discoloration of urine (orange-red) (100%)
- Pruritus (1-3%)
- Hemolytic anemia (especially in G6PD deficiency)
- Methemoglobinemia
- Hepatic toxicity
- Renal impairment
- Yellow discoloration of skin or sclera
- Allergic reactions including rash, fever, and anaphylaxis
Monitoring Parameters
- Urine color (expected orange-red discoloration)
- Signs of hemolytic anemia: fatigue, pallor, shortness of breath
- Signs of methemoglobinemia: cyanosis, chocolate-brown colored blood, hypoxia
- Hepatic function (if long-term use considered)
- Renal function (baseline and periodically if used beyond 2 days)
- Resolution of urinary symptoms
- Signs of underlying UTI progression (fever, flank pain)
Patient Education
- This medication will turn your urine orange-red; this is normal and not harmful
- It may stain clothing; sanitary pads may help prevent staining
- Do not wear contact lenses during treatment as they may become permanently stained
- This medication only relieves symptoms—it does not treat the infection
- Complete the full course of antibacterial medication prescribed for your infection
- Report any yellowing of skin or eyes, unusual fatigue, or difficulty breathing immediately
- Do not use for more than 2 days without consulting your healthcare provider
- Take with food to reduce stomach upset
- Inform all healthcare providers you are taking this medication, especially before diagnostic tests
References
1. Micromedex® Solutions. Phenazopyridine Hydrochloride. Truven Health Analytics, Inc. 2023. 2. Lexicomp Online®. Phenazopyridine: Drug Information. UpToDate, Inc. 2023. 3. American Society of Health-System Pharmacists. AHFS Drug Information®. Phenazopyridine Hydrochloride. 2023. 4. Pharmaceuticals M. Pyridium® (phenazopyridine hydrochloride) prescribing information. 2022. 5. Hooton TM. Acute uncomplicated urinary tract infection in women. New England Journal of Medicine. 2003;349(3):259-266. 6. Johnson JR. Urinary tract infections in women: diagnosis and management. American Family Physician. 2005;72(2):297-302. 7. FDA Approved Drug Products: Pyridium (phenazopyridine hydrochloride) tablets. Accessed January 2023.