Phenazopyridine

Medical uses

Phenazopyridine is prescribed for its local analgesic effects on the urinary tract. It is sometimes used in conjunction with an antibiotic or other anti-infective medication at the beginning of treatment to help provide immediate symptomatic relief. Phenazopyridine does not treat infections or injury; it is only used for symptom relief during a UTI, following surgery, or injury to the urinary tract. It is recommended that it be used for no longer than the first two days of antibacterial treatment, as longer treatment cannot kill bacteria and may mask symptoms.

Phenazopyridine is prescribed for other cases requiring relief from irritation or discomfort during urination; for example, after the use of an in-dwelling Foley catheter, endoscopic (cystoscopy) procedures, or after urethral, prostate, or urinary bladder surgeries that may result in irritation of the epithelial lining of the urinary tract.

Side effects

Phenazopyridine produces a vivid color change in urine, typically to a dark orange to reddish color. This effect is common and harmless and indeed a key indicator of the presence of the medication in the body. Users of phenazopyridine are warned not to wear contact lenses, as phenazopyridine has been known to permanently discolor them. Furthermore, it tends to leave an orange-yellow stain on surfaces (including fabrics) it comes in contact with. These color changes can be concerning for patients, who may mistake them for the presence of blood in the urine.

Phenazopyridine can cause headaches, upset stomach (especially when not taken with food), or dizziness. Less frequently it can cause a noticeable yellowish pigment change in the skin or eyes. This is due to a depressed excretion via the kidneys causing a buildup of the medication in the skin, and normally indicates a need to discontinue usage.

Phenazopyridine should be avoided by people with glucose-6-phosphate dehydrogenase deficiency, because it can cause hemolysis (destruction of red blood cells) due to oxidative stress. It has been reported to cause methemoglobinemia after overdose and even normal doses. In at least one case, the patient had pre-existing low levels of methemoglobin reductase, which likely predisposed her to the condition. It has also been reported to cause sulfhemoglobinemia.

Phenazopyridine is an azo dye. Other azo dyes, which were previously used in textiles, printing, and plastic manufacturing, have been implicated as carcinogens that can cause bladder cancer. While phenazopyridine has never been shown to cause cancer in humans, evidence from animal models suggests that it is potentially carcinogenic.

Pregnancy

This medication has shown no adverse events in animal models, but no human trials have been conducted. It is not known if phenazopyridine is excreted in breast milk.

Pharmacokinetics

The full pharmacokinetic properties of phenazopyridine have not been determined. It has mostly been studied in animal models, but they may not be very representative of humans.

Mechanism of action

Phenazopyridine's mechanism of action is not well known, and only basic information on its interaction with the body is available. It is known that the chemical has a direct topical analgesic effect on the mucosa lining of the urinary tract. It is rapidly excreted by the kidneys directly into the urine. Hydroxylation is the major form of metabolism in humans, and the azo bond is usually not cleaved. On the order of 65% of an oral dose will be secreted directly into the urine chemically unchanged.

Brand names

In addition to its generic form, phenazopyridine is distributed under the following brand names:

• Azo-Maximum Strength
• Azo-Standard
• Baridium
• Nefrecil
• Nexurin
• Phenazalgin
• Phenazo
• Phenazodine
• Pyridiate
• Pyridium
• Pyridium Plus
• Sedural
• Uricalm
• Uristat
• Uropyrine
• Urodine
• Urogesic
• Urovit

References

References

1. "The Top 300 of 2023".
2. "Phenazopyridine Drug Usage Statistics, United States, 2014 - 2023".
3. "Pyridium Plus Tablets".
4. "PYRIDIUM (phenazopyridine) tablet, film coated".
5. (April 1969). "Urinary tract infections". British Medical Journal.
6. "Phenazopyridine: MedlinePlus Drug Information". American Society of Health-System Pharmacists, Inc..
7. (1983). "Phenazopyridine-induced hemolytic anemia in a patient with G6PD deficiency". Acta Haematologica.
8. (November 1987). "Phenazopyridine-induced hemolytic anemia in G-6-PD deficiency". Drug Intelligence & Clinical Pharmacy.
9. (September 1982). "Acute hemolytic anaemia due to phenazopyridine hydrochloride in G-6-PD deficient subject". Lancet.
10. (October 2005). "Diagnosis and management of G6PD deficiency". American Family Physician.
11. (February 1982). "Acquired methemoglobinemia and hemolytic anemia after usual doses of phenazopyridine". Drug Intelligence & Clinical Pharmacy.
12. (August 1983). "Phenazopyridine induced methaemoglobinaemia associated with decreased activity of erythrocyte cytochrome b5 reductase". Journal of Medical Genetics.
13. (April 2009). "Acrocyanosis from phenazopyridine-induced sulfhemoglobinemia mistaken for Raynaud phenomenon". Journal of Clinical Rheumatology.
14. (June 2005). "Phenazopyridine-induced sulfhemoglobinemia". The Annals of Pharmacotherapy.
15. {{EMedicine. article. 778670. Cystitis in Females. treatment
16. "Phenazopyridine Hydrochloride". The American Society of Health-System Pharmacists.
17. {{EMedicine. article. 381323. Transitional Cell Carcinoma Imaging
18. (March 1993). "Metabolism of phenazopyridine by isolated rat hepatocytes". Biopharmaceutics & Drug Disposition.
19. (April 1990). "Excretion of phenazopyridine and its metabolites in the urine of humans, rats, mice, and guinea pigs". Journal of Pharmaceutical Sciences.