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Phenazopyridine

Phenazopyridine hydrochloride is a urinary analgesic, an azo dye excreted in the urine that acts topically on the urothelium to blunt the pain, burning, urgency, and frequency caused by infection, trauma, endoscopic instrumentation, catheter passage, or the passage of sounds and bougies.[1] For the reconstructive urologist and urogynecologist it is a short-term bridge analgesic, useful in the 24–48 hours before empiric antibiotics take hold for a symptomatic UTI, after office cystoscopy, following dilation or DVIU, before office intradetrusor onabotulinumtoxinA injection for procedural pain[8] and, as an off-label extrapolation, after injection for transient dysuria[1], and around urethral-sound or transurethral-catheter procedures, and never a substitute for definitive therapy. Phenazopyridine remains widely used for brief symptom relief, although modern comparative evidence is limited. In a sponsor-funded, single-blind RCT of 315 adults with dysuria that excluded urethral stricture and complicated UTI, methenamine–methylthioninium produced complete pain relief by 24 hours in 16% versus 3.31% with phenazopyridine; the 72-hour pain difference was not statistically significant, and most baseline cultures were negative.[28] The cited US prescription product is listed as unapproved drug other; DailyMed listing does not itself establish FDA approval.[1]

For the broader analgesic landscape (NSAIDs, opioids, adjuncts), see NSAIDs & analgesics. For the central-neuromodulation comparators, see Gabapentinoids, SNRIs, and TCAs.

Mechanism of Action​

Phenazopyridine is an azo dye; its pharmacokinetic properties have not been formally characterized, but the drug and its metabolites are rapidly cleared through the kidneys, where it exerts a topical analgesic effect on the urothelial mucosa.[1] The precise molecular target was historically unknown.

A 2023 electrophysiology study (Luyts et al, Eur J Pharmacol) found TRPM8 inhibition in cells and mouse sensory neurons, a plausible but unvalidated mechanism for urinary analgesia.[2]

  • TRPM8: a cold- and menthol-sensitive cation channel expressed on bladder afferent C- and Aδ-fibers, upregulated in painful bladder disorders (bladder pain syndrome / interstitial cystitis, OAB).
  • Phenazopyridine rapidly and reversibly inhibits TRPM8 in vitro (IC₅₀ 2–10 μM). Reported urine concentrations after therapeutic dosing (100–300 μM) exceed that range, but receptor exposure and target engagement in patients remain unknown.[2][14]
  • At 10 μM it does not significantly block other pain-relevant TRP channels (TRPA1, TRPV1, TRPM3), suggesting relative selectivity.

Agents in This Class​

Generic NameBrand Name(s)StrengthAvailabilityNotes
Phenazopyridine HClPyridium, Azo-Standard, Uristat, AZO Urinary Pain Relief95–99.5 mg (OTC); 100 mg, 200 mg (Rx)[25][6][24]OTC & RxAzo dye; orange-red urinary discoloration is expected with use[1]

Product names, strengths and availability vary; verify the actual dispensed product and its instructions.

Indications in Reconstructive Urology​

Phenazopyridine is purely symptomatic; it neither treats infection nor modifies disease.[1] Its role in reconstructive and functional practice is narrow and tactical:

ScenarioRationale
Symptomatic UTI, first 24–48 h of empiric antibioticsProvides symptom relief while antibacterial therapy takes effect[1][3]
Post-office cystoscopy / flexible ureteroscopyBlunts post-procedure dysuria; endoscopic procedures are a labeled indication[1]
Post-urethral dilation or DVIUShort-term analgesia during the high-irritation window
After passage of sounds, bougies, or transurethral catheter placementDescribed use in the product labeling[1]
Selected women with symptomatic recurrent uncomplicated UTI awaiting culture resultsUrinary analgesics may be reasonable while awaiting culture results in select patients when safety is not compromised. The 2025 AUA/CUA/SUFU guideline excludes women with anatomic or functional urinary abnormalities and those with rUTI due to self-catheterization or an indwelling catheter.[4] Symptom relief does not replace indicated culture-directed antibacterial therapy.[1]
Office intradetrusor onabotulinumtoxinAPreprocedure 200 mg was noninferior to intravesical lidocaine for pain in one RCT of women with idiopathic OAB[8]; also used as a bridge for transient post-injection dysuria (off-label)
Ureteral-efflux visualization at cystoscopyUrine dye for white-light cystoscopy — see below
Suspected ureterovaginal versus vesicovaginal fistulaFor a double-dye test, oral phenazopyridine colors renal urine orange and retrograde blue bladder filling colors bladder urine. Orange vaginal swab staining supports ureteric leakage, blue supports bladder leakage, and both colors support concurrent fistulas; check for blue backflow at the meatus.[29]
IC/BPS flaresOccasional symptomatic adjunct; the AUA IC/BPS guideline names phenazopyridine only among over-the-counter self-care products (Statement 10) and "urinary analgesics" within general pain management (Statement 13), both Clinical Principles without an evidence-strength grade.[23] The two-day limit applies when phenazopyridine is combined with an antibacterial for UTI.[1]

Phenazopyridine is not an alternative to antibiotics for UTI, not a chronic-use analgesic, and not a treatment for inflammatory or neoplastic urothelial disease.

Dosing & Administration​

FormulationDoseFrequencyKey rule
200 mg tablet1 tabletTID after mealsDiscontinue when symptoms controlled[1]
100 mg tablet2 tabletsTID after mealsEquivalent to 200 mg TID[1][24]
OTC (95–99.5 mg)Per product labeling; one maximum-strength brand (99.5 mg) directs 2 tablets TID with a full glass of water, adults and children ≥12 y[6]TIDNot more than 2 days (12 tablets) without a clinician[6]

The 2-day rule: when given concomitantly with an antibacterial for UTI, duration should not exceed 2 days; there is no evidence of added benefit beyond that and prolonged exposure increases the risk of accumulation-related adverse effects.[1]

Phenazopyridine can relieve symptoms while an antibacterial takes effect; in selected women with recurrent uncomplicated UTI, urinary analgesics may be used while awaiting culture when patient safety is not compromised. Do not let symptom relief delay diagnosis or indicated treatment, and discontinue phenazopyridine when symptoms are controlled.[1][4] Empiric chronic use masks infection, delays culture-directed treatment, and exposes the patient to accumulation risk.

Contraindications & Precautions​

Absolute contraindications[1]

  • Renal insufficiency. Renal elimination means that impaired clearance leads to drug accumulation and disproportionate toxicity
  • Hypersensitivity to phenazopyridine or product ingredients
  • The cited product also lists severe liver disease, severe hepatitis and pyelonephritis of pregnancy; consult the actual product label
  • OTC labeling is more conservative: ask a doctor first with kidney or liver disease, and do not use with G6PD deficiency unless a physician approves[6]

Use with caution[1]

  • Advanced age. Age-related decline in eGFR effectively reduces clearance
  • G6PD deficiency. The label warns of oxidative hemolysis and hemolytic anemia. In an Israeli database of 31,962 G6PD-deficient people, one hemolysis hospitalization was suspected to be phenazopyridine-associated; among those without such a hospitalization, 1,707 had filled phenazopyridine prescriptions. This does not exclude milder hemolysis or remove the label precaution.[1][9]
  • GI disturbances. Label advises cautious use
  • Pregnancy. Formerly Category B; no adequate human studies, use only if clearly indicated
  • Nursing. It is unknown whether phenazopyridine or its metabolites enter human milk.[1] LactMed advises avoiding phenazopyridine while breastfeeding, especially when the infant is younger than 1 month or has G6PD deficiency, because of possible methemoglobinemia, sulfhemoglobinemia, and hemolytic anemia.[18]

Clinical warning signs that mandate discontinuation[1]

  • Yellowish tinge of skin or sclera (suggests accumulation due to impaired renal excretion)
  • Any systemic dermatologic or hematologic reaction

Adverse Reactions & Overdose​

CategoryDetails
Reported; frequency not establishedHeadache, rash, pruritus, nausea, vomiting, diarrhea[1]
HematologicMethemoglobinemia requires urgent emergency/toxicology assessment; treatment depends on symptoms, level, renal function and G6PD status. A case report describes methemoglobinemia after 200 mg TID for 14 days.[19] Hemolytic anemia (Heinz bodies and bite cells on smear are described in case reports) and sulfhemoglobinemia are also reported.[1]
Renal / hepaticRenal and hepatic toxicity, usually with overdose; hypersensitivity hepatitis and jaundice also reported[1]
Dermatologic / otherYellow skin/scleral tinge (accumulation); rare anaphylactoid reactions; visual disturbance, renal calculi and aseptic meningitis are listed; tooth discoloration if tablets are crushed or held in the mouth[1]
Neoplasia (long-term exposure)The cited label describes phenazopyridine as reasonably anticipated to be a human carcinogen based on animal data; long-term dosing produced rat colorectal and female-mouse liver tumors. Human evidence is inadequate; one limited cohort of 2,214 exposed patients followed at least 3 years found no significant excess, so human risk remains unresolved.[1]

Methylene-blue paradox: the treatment for phenazopyridine-induced methemoglobinemia is itself a dye the reconstructive urologist may recognize from intraoperative use; see Methylene blue. PROVAYBLUE is contraindicated in G6PD deficiency.[5] Methylene-blue dosing must follow its specific label and account for serotonergic medicines and renal function. Oral vitamin C is not an interchangeable rapid rescue for severe symptomatic methemoglobinemia; involve toxicology or hematology for alternative treatment.

Perioperative Considerations​

  • Review perioperative use with the surgical team. Urinary discoloration can affect interpretation; no fixed preoperative stopping interval is established.
  • Urinalysis interference. Phenazopyridine's orange-red color can interfere with colorimetric, photometric or fluorometric assays. The label names urine ketones, bilirubin, glucose (glucose-oxidase), albumin (reagent strips), urobilinogen, porphyrins and urinary steroids, and color-based urinalysis generally; stool color tests are also affected.[1] Inform the laboratory; use appropriate microscopy or culture and clinical assessment. Do not delay evaluation of suspected infection or bleeding for an arbitrary washout.
  • Clothing and contact-lens staining. Counsel patients specifically about contact-lens staining; staining of contact lenses has been reported, and the OTC label warns of soft-lens staining from handling tablets.[1][6]
  • Post-endoscopic or post-dilation use. The label describes symptom relief after endoscopic procedures.[1] In one RCT of women receiving office 100-U onabotulinumtoxinA for idiopathic OAB, preprocedure oral phenazopyridine was noninferior to intravesical lidocaine for procedural pain.[8]
  • Pregnancy. The OTC label recommends a pregnancy test and clinician consultation before use in women who may be pregnant.[6]
  • Catheter aftercare. The label describes symptomatic relief after catheter passage. In a blinded RCT after gynecologic surgery, routine phenazopyridine did not improve bladder or overall pain or analgesic use (112 treated versus 107 placebo).[1][15] A 24–48-hour course after difficult passage through an atrophic or strictured urethra remains a case-by-case option.[1][15]

Ureteral-Efflux Visualization at Cystoscopy​

Oral phenazopyridine turns urine orange for white-light cystoscopy, but a four-arm randomized trial (44 allocated per group) did not demonstrate a statistically significant ureteral-jet visibility benefit over saline (p = 0.391); 10% dextrose and intravenous fluorescein did improve visibility versus saline.[26] Use is off-label. At cystoscopy during prolapse repair, visible bilateral efflux does not exclude delayed thermal injury, and the bladder and urethra also require systematic inspection.[27] Preoperative studies used 200 mg by mouth, but excretion timing varies; among the seven women given phenazopyridine in a 12-woman cohort, catheter urine first showed dye a median 70 minutes after dosing (range 59–127 minutes).[7] Give the dose with sufficient time before planned cystoscopy and keep a rescue dye available.[7][11] Check labeled contraindications, including renal insufficiency, severe liver disease and severe hepatitis; assess G6PD deficiency before dosing.[1][6]

StudyDesignFinding
Cohen 2017[7]Prospective cohort, pelvic reconstruction, n = 12 (7 phenazopyridine, 5 IV fluorescein)Median time from dosing to visible color in catheter urine: 70 min (range 59–127) after 200 mg PO given 1 h before surgery, versus 5 min (3–9) after intraoperative IV fluorescein
Propst 2016[10]RCT, n = 104, phenazopyridine vs nothingTime to visualize efflux did not differ (2 min 53 s vs 2 min 40 s; p = 0.77); surgeons reported less frustration. Fewer treated patients failed the postoperative voiding trial (9/47 vs 19/49), an exploratory secondary finding
Grimes 2017[22]Unblinded four-arm RCT, n = 130 (33 phenazopyridine, 32 IV fluorescein, 32 mannitol, 33 saline)Surgeons rated mannitol highest on the primary satisfaction scale (median 0 vs 48 for phenazopyridine; lower is better); cystoscopy time and time to confidence in jets did not differ.
Strom 2019[11]Retrospective, n = 207Phenazopyridine alone enabled visualization of ureteral flow in 190/207 (91.8%); a 200 mg dose was associated with greater effectiveness than 100 mg; the 17 failures needed rescue fluorescein
Stanley 2022[12]Three-arm RCT, n = 84 (placebo, riboflavin, phenazopyridine)Urine staining was more intense with phenazopyridine than with riboflavin or placebo

Plan the dose timing, because onset can be slow and variable, and keep a rapid agent such as sodium fluorescein available when efflux is not seen. See the visualization agents hub for agent comparison.

Evidence Summary​

IndicationEvidence LevelKey SourceNotes
Acute symptomatic UTI bridge analgesiaThree published randomized reports: one blinded single-dose study (n = 60) and two open-label reports (n = 152 and n = 440)Petrov 2020[16]; Davidov et al. 2021[21]; Zaitsev and Davidov 2025[17]; product labeling[1]; Zelenitsky-Zhanel review[3]The 2020 trial measured symptom relief at six hours before antibiotics. The 2021 report compared fosfomycin plus phenazopyridine with fosfomycin plus drotaverine (76 women per arm) through day six; the 2025 report found faster pain and dysuria relief through day six. These reports do not change the label's two-day limit when phenazopyridine is combined with an antibacterial for UTI.
Post-procedural dysuria (cystoscopy, dilation, catheter, sounds)One randomized cystoscopy trial (n = 97); labeling for endoscopic procedures, sounds and catheters; dilation by extrapolationTsukanov 2020[20]; product labeling[1]With lidocaine gel in both arms, the randomized trial found lower pain immediately and at 3 hours after cystoscopy with phenazopyridine (50 vs 47 patients). A separate blinded postoperative trial in catheterized gynecologic patients found no improvement in bladder pain, overall pain, or analgesic use (112 phenazopyridine versus 107 placebo).[15]
Preprocedure analgesia, office onabotulinumtoxinASingle RCT (n = 100 analyzed)Stewart 2022[8]Noninferior to lidocaine instillation; clear visualization 89.4% vs 100%; shorter room time
Prolonged use (>14 days), radiation cystitisRetrospective matched cohort (90 pairs)Shore 2020[13]13 versus 18 recorded adverse drug reactions among 90 matched patients per group (p = 0.32)
TRPM8 mechanismPreclinical (in vitro)Luyts 2023[2]—
Chronic use / disease modificationNot supportedProduct labeling[1]Discontinue when symptoms controlled
rUTI preventionNot an indicationProduct labeling[1]Symptomatic only — see UTI suppressive & prophylactic

Practical Pearls​

  • For eligible adults, 200 mg TID after meals for no more than 2 days with UTI treatment is a common prescription-label regimen; check contraindications and the actual product first.[1]
  • Counsel about urine color up front. Patients who see orange-red urine without warning present to the ED thinking they are bleeding; patients who are warned are unconcerned.
  • Warn about contact lenses. Soft lenses can stain; recommend glasses for the duration of therapy and hand-washing after touching tablets.
  • Check renal function before prescribing in the elderly. The most common preventable harm is accumulation in unrecognized CKD.
  • Review known G6PD deficiency and prior hemolysis in every patient; a short course does not eliminate the hemolysis risk.
  • Tell the laboratory about use. Some strip-based or color-based results can be unreliable, while clinical assessment, microscopy and culture may still be needed.
  • The 2-day rule exists for a reason. The label states there is no evidence of additional benefit beyond 48 hours with an antibacterial. Toxicity (methemoglobinemia, hemolysis, renal and hepatic injury) is linked to overdose and impaired clearance, so older patients and CKD carry the most risk.
  • It is not a disease-modifying treatment for IC/BPS.[1] The AUA guideline lists phenazopyridine among OTC self-care options and allows urinary analgesics for pain management, without specifying a chronic phenazopyridine regimen[23]; patients who have been self-medicating with OTC AZO for years should be redirected to the AUA IC/PBS framework.

See Also​

References​

1. Phenazopyridine hydrochloride tablets: product labeling. DailyMed, updated July 27, 2026; marketing category unapproved drug other. Label.

2. Luyts N, Daniluk J, Freitas ACN, et al. "Inhibition of TRPM8 by the urinary tract analgesic drug phenazopyridine." Eur J Pharmacol. 2023;942:175512. doi:10.1016/j.ejphar.2023.175512

3. Zelenitsky SA, Zhanel GG. "Phenazopyridine in urinary tract infections." Ann Pharmacother. 1996;30(7-8):866–868. doi:10.1177/106002809603000727

4. AUA/CUA/SUFU. Recurrent uncomplicated urinary tract infections in women guideline. 2025. Guideline.

5. PROVAYBLUE (methylene blue injection): US prescribing information. DailyMed label. Accessed September 12, 2026.

6. AZO Urinary Pain Relief Maximum Strength (phenazopyridine HCl 99.5 mg): OTC drug facts. i-Health. DailyMed label. Accessed September 24, 2026.

7. Cohen SA, Chaudhry Z, Oliver JL, et al. Comparison of Times to Ureteral Efflux after Administration of Sodium Fluorescein and Phenazopyridine. J Urol. 2017;197(2):519-523. doi:10.1016/j.juro.2016.07.099

8. Stewart LE, Siddique M, Jacobs KM, et al. Oral phenazopyridine vs intravesical lidocaine for bladder onabotulinumtoxinA analgesia: a randomized controlled trial. Am J Obstet Gynecol. 2022;227(2):308.e1-308.e8. doi:10.1016/j.ajog.2022.05.025

9. Gronich N, Rosh B, Stein N, et al. Medications and Acute Hemolysis in G6PD-Deficient Patients - A Real-World Study. Clin Pharmacol Ther. 2024;116(6):1537-1543. doi:10.1002/cpt.3333

10. Propst K, Tunitsky-Bitton E, O'Sullivan DM, Steinberg AC, LaSala C. Phenazopyridine for Evaluation of Ureteral Patency: A Randomized Controlled Trial. Obstet Gynecol. 2016;128(2):348-355. doi:10.1097/AOG.0000000000001472

11. Strom EM, Chaudhry ZQ, Guo R, et al. Effectiveness of Assessing Ureteral Patency Using Preoperative Phenazopyridine. Female Pelvic Med Reconstr Surg. 2019;25(4):289-293. doi:10.1097/SPV.0000000000000540

12. Stanley R, deRiese C, Almekdash MH. Urine staining intensity and observation of intraoperative ureteral jets among oral agents. Int Urogynecol J. 2022;33(9):2427-2433. doi:10.1007/s00192-021-04867-y

13. Shore SN, Britnell SR, Brown JN. Safety analysis of long-term phenazopyridine use for radiation cystitis. J Oncol Pharm Pract. 2020;26(2):306-311. doi:10.1177/1078155219842646

14. Clark A, Bourlotos G, Elmasri M, Grundy L. "Phenazopyridine inhibits bladder mechanosensory signalling via the bladder lumen." Eur Urol Open Sci. 2025;76:14–16. doi:10.1016/j.euros.2025.04.001

15. Anderson C, Chimhanda M, Sloan J, Galloway S, Sinacore J, Brubaker L. "Phenazopyridine does not improve catheter discomfort following gynecologic surgery." Am J Obstet Gynecol. 2011;204(3):267.e1–267.e3. doi:10.1016/j.ajog.2010.12.045

16. Petrov SB, Slesarevskaya MN, Chibirov KH, Topuzov ME, Kagan OF, Voronova EN. "Efficiency and safety of phenazopyridine for treatment of uncomplicated urinary tract infection: results of multi-center, randomized, placebo-controlled, clinical study." Urologiia. 2020;(3):15–21. doi:10.18565/urology.2020.3.15-21

17. Zaitsev AV, Davidov MI. "Results of treatment of acute uncomplicated cystitis in 440 women of working age in a large industrial city." Urologiia. 2025;(2):35–43. PMID:40377579 doi:10.18565/urology.2025.2.35-43

18. National Institute of Child Health and Human Development. "Phenazopyridine." Drugs and Lactation Database (LactMed). Updated October 31, 2018. NCBI Bookshelf

19. Joseph J, Sundararaj JJ, Shekinah S, Kamalakannan S. "Rare cause of dyspnoea: phenazopyridine-induced methemoglobinemia." BMJ Support Palliat Care. 2024;14(e2):e1792–e1794. doi:10.1136/spcare-2023-004692

20. Tsukanov AY, Makushin DG, Mirzakadiev AA, Zolotov IA. "Influence of phenazopyridine on the well-being of patients during and after cystoscopy." Urologiia. 2020;(4):50–54. doi:10.18565/urology.2020.4.50-54

21. Davidov MI, Meltsina MN, Bunova NE, Metelkin AM, Prussakov OR, Lunev AA. "Phenazopyridine and fosfomycin for the acute cystitis treatment: results of multicenter randomized study." Urologiia. 2021;(3):20–27. doi:10.18565/urology.2021.3.20-27

22. Grimes CL, Patankar S, Ryntz T, et al. "Evaluating ureteral patency in the post-indigo carmine era: a randomized controlled trial." Am J Obstet Gynecol. 2017;217(5):601.e1–601.e10. doi:10.1016/j.ajog.2017.07.012

23. American Urological Association. Diagnosis and Treatment of Interstitial Cystitis/Bladder Pain Syndrome: AUA Guideline. 2022. Guideline

24. Winder Laboratories, LLC. Phenazopyridine hydrochloride tablets, USP (100 mg and 200 mg): product labeling. Rev. Dec. 2021; DailyMed updated May 31, 2022. Label

25. Drug Ocean LLC. Phenazopyridine hydrochloride tablets, 95 mg: OTC drug facts. DailyMed. Label.

26. Espaillat-Rijo L, Siff L, Alas AN, et al. "Intraoperative Cystoscopic Evaluation of Ureteral Patency: A Randomized Controlled Trial." Obstet Gynecol. 2016;128(6):1378–1383. doi:10.1097/AOG.0000000000001750

27. Cohen SA, Carberry CL, Smilen SW. "American Urogynecologic Society consensus statement: cystoscopy at the time of prolapse repair." Female Pelvic Med Reconstr Surg. 2018;24(4):258–259. doi:10.1097/SPV.0000000000000529

28. Savioli Neto F, Hachul H, Pereira MA, et al. "Efficacy of methenamine with methylthioninium in the treatment of dysuria: a randomized clinical study." Int Urogynecol J. 2023;34(12):3051–3058. doi:10.1007/s00192-023-05669-0

29. Goh J, Romanzi L, Elneil S, et al. "An International Continence Society (ICS) report on the terminology for female pelvic floor fistulas." Neurourol Urodyn. 2020;39(8):2040–2071. doi:10.1002/nau.24508