Phenazopyridine

Urinary tract analgesic, Azo dye

Phenazopyridine

Pyridium (Rx), Azo Standard, AZO Urinary Pain Relief (OTC)

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Summary

Classes

Urinary tract analgesic, Azo dye

Common uses

Symptomatic relief of urinary urgency, frequency, dysuria, and burning▲0▼, adjunctive only (does not treat the underlying infection)

Pharmacy

Starting dose

100-200 mg PO TID after meals × no more than 2 days when used with concurrent antibiotic

Preparations

95 mg (OTC), 99.5 mg, 100 mg, 200 mg tablets

US FDA Max

Limit to 48 hours of use to avoid hemolysis and methemoglobinemia

Pharmacology

Routes

Oral

Onset

Symptom relief within 30 minutes

Duration

6-8 hours

Half-life

~7-10 hours (variable; longer in renal impairment)

Bioavailability

High (oral)

Pregnancy

Limited data; not first-line in pregnancy.^{[citation needed]}

Legal status

OTC (lower doses) and Rx-only (higher doses) in US

Purported mechanism

Phenazopyridine is an azo dye with topical analgesic action on the urinary tract mucosa; the precise mechanism is not fully characterized but appears to involve local membrane effects on bladder and urethral sensory nerves.▲0▼ Produces characteristic bright orange-red discoloration of urine, sweat, tears, and contact lenses; G6PD-deficient patients are at increased risk of hemolytic anemia. Chronic high-dose use is associated with methemoglobinemia and renal/hepatic toxicity; treatment limit of 2 days is the practical safety margin.