Usage
Phenazopyridine is prescribed for the symptomatic relief of pain, burning, urgency, frequency, and other discomforts arising from irritation of the lower urinary tract mucosa. This irritation can be caused by infection, trauma, surgery, endoscopic procedures, or the passage of sounds or catheters. It is classified as a urinary tract analgesic.
Phenazopyridine’s mechanism of action is not fully understood, but it is believed to exert a local anesthetic or analgesic effect on the lining of the urinary tract.
Alternate Names
Phenazopyridine is also known by various brand names, including Pyridium, Azo-Standard, Uristat, AZO, and Prodium.
How It Works
Pharmacodynamics: Phenazopyridine exerts a topical analgesic effect on the urinary tract mucosa. The exact mechanism is not well-elucidated, but it’s thought to act locally, possibly by interfering with mucosal sensory transduction.
Pharmacokinetics:
- Absorption: Phenazopyridine is well-absorbed after oral administration, preferably taken with or after meals.
- Metabolism: It undergoes hepatic metabolism, producing potentially active and/or toxic metabolites.
- Elimination: Primarily eliminated renally as unchanged drug and metabolites.
The mode of action at the cellular level is not fully understood; receptor binding, enzyme inhibition, or neurotransmitter modulation haven’t been clearly identified. Renal excretion is the main elimination pathway.
Dosage
Standard Dosage
Adults:
200 mg three times a day after meals. Maximum daily dose is 600 mg. When used concomitantly with an antibiotic for a urinary tract infection (UTI), the duration of phenazopyridine use should not exceed two days.
Children:
Children aged 6 to 11 years: 4 mg/kg three times a day after meals, not exceeding two days when used with an antibiotic for UTI. Safety and effectiveness have not been established in children under 6.
Special Cases:
- Elderly Patients: Dosage adjustment may be necessary due to potential age-related decline in renal function.
- Patients with Renal Impairment: Contraindicated in patients with creatinine clearance <50 mL/min. For CrCl 50-80 mL/min, the interval between doses should be increased to every 8–16 hours.
- Patients with Hepatic Dysfunction: Dosage adjustment is recommended due to hepatic metabolism of the drug, although specific guidelines aren’t available.
- Patients with Comorbid Conditions: Caution in patients with G6PD deficiency due to increased risk of hemolytic anemia and methemoglobinemia.
Clinical Use Cases
Phenazopyridine is specifically indicated for symptomatic relief of urinary tract discomfort and not for other clinical scenarios such as intubation, surgical procedures, mechanical ventilation, or ICU use. It plays no role in the management of emergency situations.
Dosage Adjustments
Dose adjustments are necessary for renal impairment as described above. No specific dosage adjustments are available for hepatic dysfunction or other metabolic disorders.
Side Effects
Common Side Effects
Headache, dizziness, stomach upset, discoloration of urine (orange to red).
Rare but Serious Side Effects
Methemoglobinemia, hemolytic anemia, acute renal failure, hepatic toxicity, jaundice.
Long-Term Effects
No specific long-term effects associated with short-term use; prolonged use is not recommended.
Adverse Drug Reactions (ADR)
As above, methemoglobinemia, hemolytic anemia, acute renal failure, and hepatic toxicity require immediate intervention.
Contraindications
Renal insufficiency, severe hepatitis, hypersensitivity to phenazopyridine.
Drug Interactions
No clinically significant drug interactions have been reported.
Pregnancy and Breastfeeding
Pregnancy Safety Category B. Animal studies have not shown fetal harm, but there are no adequate and well-controlled studies in pregnant women. Use during pregnancy only if clearly needed. It is unknown whether phenazopyridine is excreted in breast milk.
Drug Profile Summary
- Mechanism of Action: Local analgesic effect on the urinary tract mucosa.
- Side Effects: Headache, dizziness, stomach upset, urine discoloration. Rarely: methemoglobinemia, hemolytic anemia, acute renal failure, hepatic toxicity.
- Contraindications: Renal insufficiency, severe hepatitis, hypersensitivity.
- Drug Interactions: None known.
- Pregnancy & Breastfeeding: Category B; use only if clearly needed. Excretion in breast milk unknown.
- Dosage: Adults: 200 mg TID after meals, max 2 days for UTI. Children (6-11): 4 mg/kg TID after meals, max 2 days for UTI.
- Monitoring Parameters: Observe for signs of methemoglobinemia, hemolytic anemia, and hepatic or renal dysfunction. Monitor urine output and color.
Popular Combinations
Often used concomitantly with antibiotics for the initial two days of UTI treatment.
Precautions
Avoid in patients with renal impairment or severe liver disease. Discontinue if signs of hemolytic anemia, methemoglobinemia, or hepatic/renal dysfunction appear. Do not use for more than two days for UTI treatment alongside antibiotics.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Phenazopyridine?
A: Adults: 200 mg three times a day after meals for a maximum of two days when treating a UTI alongside an antibiotic. Children (6-11): 4 mg/kg three times a day after meals, also for a maximum of two days for UTI treatment alongside an antibiotic. Adjust for renal impairment.
Q2: How does Phenazopyridine work?
A: It acts as a local analgesic on the urinary tract mucosa, relieving pain and discomfort.
Q3: What are the common side effects?
A: Headache, dizziness, stomach upset, and red-orange urine discoloration.
Q4: Can Phenazopyridine cure a UTI?
A: No. It only treats the symptoms, not the infection itself. Antibiotics are necessary to treat the underlying infection.
Q5: What are the serious side effects to watch for?
A: Methemoglobinemia, hemolytic anemia, acute renal failure, and hepatic toxicity.
Q6: Who shouldn’t take Phenazopyridine?
A: Patients with renal insufficiency or severe liver disease, as well as those with a hypersensitivity to the drug.
Q7: Can pregnant women take Phenazopyridine?
A: It’s a Pregnancy Category B drug, meaning animal studies haven’t shown harm, but there are no well-controlled studies in humans. Use only if clearly needed and under the supervision of a physician.
Q8: How long can you take Phenazopyridine?
A: No more than two days when used with an antibiotic for a UTI. For other causes of urinary discomfort, consult a physician for duration.
Q9: Does Phenazopyridine interact with other medications?
A: No clinically significant drug interactions have been reported.
Q10: Will Phenazopyridine change the color of my urine?
A: Yes, it can turn urine orange or red. This is a normal side effect and not harmful.
