Pyridium - Drug Monograph

Introduction

Phenazopyridine hydrochloride, commonly known by its brand name Pyridium, is a urinary analgesic medication used to relieve symptoms associated with urinary tract irritation. First introduced in the 1920s, it provides local analgesic effects on the urinary tract mucosa without treating the underlying infection or pathology.

Mechanism of Action

Pyridium exerts a local analgesic effect on the urinary tract mucosa through an unknown exact mechanism. It is thought to interfere with the sensory perception of pain and discomfort in the urinary tract by acting on the mucosal nerve endings. 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 urinary tract irritation
• Adjunctive therapy in urinary tract infections, cystitis, urethritis, and following urologic procedures
• Relief of symptoms during diagnostic procedures involving the urinary tract

Dosage and Administration

• Administer with or after meals to minimize gastric upset
• Tablets should be swallowed whole with a full glass of water
• Discontinue use when pain and discomfort subside

• Renal impairment: Contraindicated in patients with renal insufficiency
• Hepatic impairment: Use with caution
• Geriatric patients: Consider reduced renal function
• Pediatric use: Not recommended for children under 6 years

Pharmacokinetics

Contraindications

• Renal insufficiency (glomerular filtration rate <50 mL/min)
• Hypersensitivity to phenazopyridine or any component of the formulation
• Hepatitis
• Severe renal or hepatic impairment
• Glucose-6-phosphate dehydrogenase (G6PD) deficiency

Warnings and Precautions

• May cause hemolytic anemia, particularly in patients with G6PD deficiency
• Renal and hepatic toxicity reported with prolonged use or overdose
• May interfere with laboratory tests based on spectrometry or color reactions
• Discontinue if skin or sclera develop yellow discoloration (may indicate accumulation)
• Use with caution in patients with pre-existing renal impairment

Drug Interactions

• Sulfonamides: May increase risk of crystalluria
• Other urinary tract medications: No significant interactions reported
• Laboratory test interference: May cause false-positive results for urinary glucose tests using Benedict's solution or Clinitest tablets

Adverse Effects

• Headache
• Dizziness
• Gastrointestinal disturbances
• Orange-red discoloration of urine (expected effect)

• Hemolytic anemia (especially in G6PD deficiency)
• Methemoglobinemia
• Hepatic toxicity
• Renal impairment
• Yellow discoloration of skin or sclera
• Allergic reactions

Monitoring Parameters

• Urinary symptoms and pain relief
• Urine color (expected orange-red discoloration)
• Complete blood count in prolonged therapy
• Renal function tests in patients at risk
• Hepatic function in long-term use
• Signs of hemolytic anemia (fatigue, pallor, dark urine)

Patient Education

• Urine will turn orange-red; this is normal and not harmful
• May stain clothing; wear protective undergarments if concerned
• Take with food to reduce stomach upset
• This medication only relieves symptoms; complete the full course of antibacterial therapy if prescribed
• Contact healthcare provider if symptoms persist beyond 2 days or worsen
• Seek immediate medical attention if skin or eyes turn yellow, or if unusual fatigue or dark urine develops
• Do not exceed recommended dosage or duration

References

1. Micromedex Solutions. Phenazopyridine Hydrochloride. Truven Health Analytics, Inc. 2023. 2. Lexicomp Online. Phenazopyridine: Drug Information. Wolters Kluwer Clinical Drug Information, Inc. 2023. 3. American Society of Health-System Pharmacists. AHFS Drug Information. Bethesda, MD. 2023. 4. Pfizer Laboratories. Pyridium (phenazopyridine hydrochloride) prescribing information. 2023. 5. Hooton TM. Clinical practice. Uncomplicated urinary tract infection. N Engl J Med. 2012;366(11):1028-1037. 6. Gupta K, Hooton TM, Naber KG, et al. International clinical practice guidelines for the treatment of acute uncomplicated cystitis and pyelonephritis in women: A 2010 update by the Infectious Diseases Society of America and the European Society for Microbiology and Infectious Diseases. Clin Infect Dis. 2011;52(5):e103-e120.