PHENAZOPYRIDINE (Pyridium, Azo): What is used for?

What is Phenazopyridine?

Phenazopyridine is an active ingredient used for the treatment of urinary tract infections, dysuria and interstitial cystitis.
The product ingredient is Phenazopyridine hydrochloride (hcl).

The brand names of Phenazopyridine in United States are: Pyridium, Azo Urinary Pain Relief, Azo-Standard and Uristat.

Mechanism of action (MOA) of Phenazopyridine

The mechanism of action is not known. It is only known that it is excreted in urine and that it causes an anaesthetic effect on the mucous membrane of the urinary tract.

Therapeutic Indications, Uses and Benefits of Phenazopyridine

Relieves pain, burning, irritation and discomfort in the urinary tract, as well as the need to urinate urgently and frequently, all symptoms caused by urinary tract infections, surgery, injuries or tests.

Acidifying for the treatment of symptoms of irritation of the lower urinary tract, relieves symptoms of dysuria, urinary frequency, burning and when there is urgency to urinate.

Gives urine an orange or red color.

It is an auxiliary analgesic in the treatment of urinary tract infections such as: pyelitis, pyelonephritis, urethritis, uretrotrigonitis.

As prophylaxis in preoperative and postoperative and instrumental urological examinations.

Dosage of Phenazopyridine


Adults: 200 mg every 8 hours together or after meals.
Children: 100 mg every 8 hours at the discretion of the doctor, together or after meals.

The duration of treatment is established at the discretion of the physician, when symptoms have been controlled.
Its use is not recommended for more than 15 consecutive days.


  • 95 mg/1
  • 100 mg/1
  • 200 mg/1


Contraindications of Phenazopyridine

  • Do not apply in patients with known hypersensitivity to salt and/or their metabolites.
  • Patients with renal insufficiency.
  • Oliguria.
  • Glomerulonephritis.
  • Hepatic Insufficiency.
  • Hepatitis.
  • Pyelonephritis associated with pregnancy.
  • Gastrointestinal disorders.
  • In patients with a history of enzyme deficiency methemoglobulinemia.
  • Children under 12 years of age remain under the responsibility of the physician.

Warnings and precautions

  • Possible allergy to phenazopyridine or other medications.
  • Possible interactions with other prescription or over-the-counter medications, including vitamins.
  • Caution in patients who have had or have kidney disease or G6DH deficiency.
  • Pregnancy.
  • Caution in patients with liver disease under treatment.
  • Urine turns reddish orange, which should be reported to patients.

Liver failure


Renal Insufficiency


Interactions with Phenazopyridine

Lab: May interfere with uroanalysis based on spectrometry or color reactions.
There may be disturbances in urine tests, such as determination of albumin and ketones depending on the method used.
A false positive reaction may be obtained in the glucose and porphyrin test.

Adverse reactions and side effects of Phenazopyridine

Headache, dizziness, confusion; yellowing of the skin or eyes, skin coloring (blue to blue-purple), rash; upset stomach; fever; dyspnea; sudden oliguria; swelling of the face, fingers, feet, or legs.


Source: The content of this active ingredient has been written taking into account the clinical and molecular information of all medicines authorised and marketed in the United States under the Unique Ingredient Identifier (UNII) by the Substance Registration System (SRS) of the Food and Drug Administration (FDA) and the United States Pharmacopeia (USP).

In order to know in detail the information authorized by the FDA for each drug, you should consult the corresponding medication guide authorized by the FDA.


NCI Thesaurus: C29357

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