ATC Class:G04BX06
VA Class:AM650
Phenazopyridine hydrochloride is an azo dye that exerts analgesic or local anesthetic action on the urinary tract mucosa.
Phenazopyridine is used for the symptomatic relief of pain, burning, urgency, frequency, and other discomforts resulting from irritation of the lower urinary tract mucosa caused by infection, trauma, surgery, endoscopic procedures, or the passage of sounds or catheters. The use of phenazopyridine for relief of symptoms should not delay definitive diagnosis and treatment of causative conditions. The drug is not a substitute for specific surgery or antimicrobial therapy. Phenazopyridine also may be used for self-medication for the symptomatic relief of minor pain, urgency, frequency, and burning on urination.
Combinations of phenazopyridine hydrochloride with sulfonamides are commercially available for the initial treatment of uncomplicated urinary tract infections caused by susceptible organisms when relief of symptoms of pain, burning, or urgency is needed during the first 2 days of therapy. There is a lack of evidence that combinations of phenazopyridine hydrochloride with sulfonamides provide greater benefit than a sulfonamide alone after 2 days, and treatment beyond 2 days should only be continued with a sulfonamide alone.
Phenazopyridine hydrochloride is administered orally after meals.
The usual adult dosage of phenazopyridine hydrochloride is 200 mg 3 times daily. Children may receive 12 mg/kg daily, given in 3 divided doses. The drug should be discontinued when pain and discomfort are relieved, usually after 3-15 days of phenazopyridine therapy. Treatment with combination preparations containing phenazopyridine hydrochloride and a sulfonamide should not exceed 2 days. Treatment beyond 2 days should only be continued with a sulfonamide alone. (See Uses.)
For self-medication in adults, the manufacturer recommends a phenazopyridine hydrochloride dosage of 190 mg 3 times daily for up to 2 days. If symptoms persist for longer than 2 days, a clinician should be consulted.
Phenazopyridine therapy has occasionally been associated with headache, vertigo, rash, pruritus, and mild GI disturbances. Rarely, methemoglobinemia, hemolytic anemia, skin pigmentation, and transient acute renal failure have been reported, usually in association with high dosage or prolonged therapy or acute overdosage, or with usual doses in patients with impaired renal function. A few cases of jaundice and hepatitis have occurred, probably caused by hypersensitivity. An anaphylactoid-like reaction also has been reported. Rarely, phenazopyridine has precipitated in the urine to form renal stones. Staining of contact lenses also has occurred in patients receiving the drug.
Precautions and Contraindications
The patient should be advised that phenazopyridine produces an orange to red color in the urine and may stain fabric; stains can be removed by soaking fabric in a 0.25% solution of sodium dithionate or sodium hydrosulfite.
Patients receiving phenazopyridine for self-medication should be advised to discontinue the drug and consult a clinician if pain and discomfort persist for longer than 2 days.
Phenazopyridine is contraindicated in patients with glomerulonephritis, severe hepatitis, uremia, pyelonephritis during pregnancy, or impaired renal function. A yellowish color of the skin or sclerae may indicate accumulation of phenazopyridine resulting from renal impairment, and necessitates discontinuance of the drug.
Animal studies have shown phenazopyridine to be a possible carcinogen, but the risk to humans in short-term therapy is believed to be negligible.
Because of its properties as an azo dye, phenazopyridine may interfere with urinalysis based on spectrometry or color reactions. Phenazopyridine may interfere with the phenolsulfonphthalein (PSP) excretion test of kidney function; butanol may be used to extract phenazopyridine from the final alkaline urine dilution to give accurate results.
Phenazopyridine may interfere with urinary glucose tests. Delayed reactions of the drug with glucose oxidase reagent (Clinistix®, Tes-Tape®) may be interpreted as false-negative reactions and occasional false-positive tests occur with Tes-Tape®; results of tests using cupric sulfate (Clinitest®) are not affected. Phenazopyridine may affect urinary bilirubin tests by giving false-positive results for the foam test and atypical color reactions with p -nitrobenzene diazonium p -toluene sulfonate reagent (Ictotest®).
Phenazopyridine may interfere with urinary ketone tests using sodium nitroprusside (Acetest®, Ketostix®) or Gerhardt ferric chloride by producing interfering colors; this can be prevented by adding a small amount of sodium dithionate to urine before performing the tests. The drug may interfere with urinary protein tests by discoloring bromophenol blue test areas of commercial reagent strips and interfering with the nitric acid ring test; the sulfosalicylic acid and heat-acetic acid tests are unaffected. Phenazopyridine may interfere with determination of urinary steroids by affecting absorbancy in the modified Glenn-Nelson method of 17-hydroxycorticosteroid determination and the Holtorff-Koch modification of the Zimmerman reaction for determining 17-ketosteroids. Phenazopyridine may interfere with urinary urobilinogen determinations because of color interference with Ehrlich's reagent. Phenazopyridine may produce falsely elevated readings in the spectrophotofluorimetric screening tests and assays for porphyrins.
Methemoglobinemia, hemolytic anemia (with or without Heinz body formation), skin pigmentation, and renal and hepatic impairment may occur following acute overdosage of phenazopyridine hydrochloride; occasionally, hepatic failure or transient, nonoliguric acute renal failure may occur. Individuals with glucose-6-phosphate dehydrogenase deficiency may be predisposed to hemolysis. Gastric contents and urine may be deeply stained.
In acute overdosage of phenazopyridine hydrochloride, the stomach should be emptied immediately by inducing emesis or by gastric lavage. If the patient is comatose, having seizures, or lacks the gag reflex, gastric lavage may be performed if an endotracheal tube with cuff inflated is in place to prevent aspiration of gastric contents. Supportive and symptomatic treatment should be initiated. IV administration of methylene blue 1-2 mg/kg should cause prompt reduction of methemoglobinemia and disappearance of cyanosis. While the manufacturer recommends 100-200 mg of oral ascorbic acid as an alternative to methylene blue, ascorbic acid reduces methemoglobinemia at a slower rate and therefore is less effective than methylene blue. Exchange transfusions have been used successfully in acute phenazopyridine overdosage in infants. Peritoneal dialysis may be useful for managing fluid and electrolyte disturbances in phenazopyridine-induced acute renal failure.
Phenazopyridine exerts analgesic or local anesthetic action on the urinary tract mucosa. The precise mechanism of action is not known. Although in vitro studies have shown phenazopyridine to inhibit the growth of staphylococci, streptococci, gonococci, and Escherichia coli, the drug imparts little or no antibacterial activity to the urine.
The pharmacokinetic properties of phenazopyridine have not been determined.
Trace amounts of phenazopyridine are believed to cross the placenta and to enter the CSF. It is not known if phenazopyridine is distributed into milk.
Metabolism of phenazopyridine probably occurs in the liver and other body tissues, but metabolites have not been identified. Phenazopyridine is rapidly excreted by the kidneys, with as much as 65% of an oral dose being excreted unchanged in urine. In one study in healthy individuals, maximum urinary excretion of phenazopyridine occurred within 5-6 hours after an oral dose, and the average time of total excretion of the drug was 20.4 hours. Small amounts of phenazopyridine were excreted in feces.
Phenazopyridine hydrochloride is an azo dye. Phenazopyridine hydrochloride occurs as a light or dark red to dark violet, crystalline powder, is odorless or has a slight odor, and is slightly soluble in water and in alcohol.
Phenazopyridine hydrochloride tablets should be stored in tight containers at 15-30°C. Commercially available phenazopyridine tablets have expiration dates of 3-5 years following the date of manufacture, depending on the tablet strength and manufacturer.
Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.
Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.
Routes | Dosage Forms | Strengths | Brand Names | Manufacturer |
|---|---|---|---|---|
Oral | Tablets | 95 mg | ||
97 mg | ||||
97.2 mg | ||||
100 mg* | Phenazopyridine Hydrochloride Tablets | |||
200 mg* | Phenazopyridine Hydrochloride Tablets | |||
Pyridium® | Warner Chilcott |
* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name
Routes | Dosage Forms | Strengths | Brand Names | Manufacturer |
|---|---|---|---|---|
Oral | Tablets | 150 mg with Butabarbital 15 mg, and Hyoscyamine Hydrobromide 0.3 mg | Pyridium® Plus |