- Adverse effects
- Food Interactions
Phenazopyridine, also known as Pyridium, is a urinary tract analgesic used for the short-term management of urinary tract irritation and its associated unpleasant symptoms such as burning and pain during urination. In the USA, this drug was previousl...
Phenazopyridine, also known as Pyridium, is a urinary tract analgesic used for the short-term management of urinary tract irritation and its associated unpleasant symptoms such as burning and pain during urination. In the USA, this drug was previously marked by Roche but has been discontinued by the FDA. It is still used in various parts of the world. Ingestion of phenazopyridine is found to change the appearance of the urine by imparting an orange or red color, as it is considered an azo dye.Read more
Phenazopyridine hydrochloride is indicated to relieve uncomfortable symptoms that occur as a consequ... Phenazopyridine hydrochloride is indicated to relieve uncomfortable symptoms that occur as a consequence of mucosal irritation of the lower urinary tract in adults. The irritation may be a result of trauma, surgery, endoscopic procedures, infection, or the insertion of instruments or urinary catheters. Phenazopyridine may be used in combination with antimicrobial therapy but is not used as an antimicrobial agent. It contributes to the relief of discomfort and pain before antimicrobial therapy begins to take effect. It is important to note that the duration of treatment with this drug should last a maximum of 2 days. Phenazopyridine is available in many countries as an over the counter drug. Read more
Phenazopyridine acts as a local anesthetic offering relief from irritating conditions of the urinary...
Phenazopyridine acts as a local anesthetic offering relief from irritating conditions of the urinary tract. It relieves urinary urgency frequency, burning, pain, and discomfort.[14,18]
**A note on urine and skin discoloration and interference with test results**
Yellowing of the skin or sclerae of the eyes may indicate that the accumulation of phenazopyridine has occurred. This may be a consequence of overdose, decreased renal function, taking the drug for over two days. Elderly patients may be at particular risk due to a decline in renal function, potentiating the risk of phenazopyridine accumulation. The drug should be discontinued if yellowing of the skin or sclerae is observed. Hemolytic anemia is a risk of phenazopyridine, especially in cases of overdose. In addition to the above effects, this drug may impart an orange or red color of urine and feces, causing staining of clothing. Other body fluids may also be stained, and in patients wearing contact lenses, phenazopyridine may cause lens staining. Due to its orange-red color, this drug may interfere with laboratory requiring colorimetric, spectrophotometric or fluorometric methods of analysis. In patients with G6PD enzyme deficiency, this drug poses a greater risk of hemolysis, even at normal doses and is not recommended.
**A note on carcinogenesis**
Based on the results of in vivo studies in rats, this drug has been listed as a carcinogen in the USA since 1981. Rats given this drug were found to demonstrate increased rates of hepatocellular carcinoma and colorectal tumors. Use this agent with caution and limit the administration of this drug when possible. Read more
Mechanism of action
The full mechanism of action of phenazopyridine is not fully elucidated[ The full mechanism of action of phenazopyridine is not fully elucidated, however, it is reported to exert a direct topical analgesic effect on the mucosal lining of the urinary tract via the inhibition of voltage-gated sodium channels and possibly group A nerve fibers, as suggested by the results of a study in rats. The above actions likely lead to the relief of unpleasant urinary symptoms. Read more
Phenazopyridine is absorbed in the gastrointestinal tract.[ Phenazopyridine is absorbed in the gastrointestinal tract.[10,20] The mean Cmax is 65.00 ± 29.23 ng/mL, the mean Tmax is 2.48 ± 0.50 h, and the mean AUC(0 – ∞)is 431.77 ± 87.82 ng.h/mL. Read more
Information currently not available.
Volume of distribution
Small, trace quantities of phenazopyridine are thought to cross the placenta and the blood-brain bar... Small, trace quantities of phenazopyridine are thought to cross the placenta and the blood-brain barrier, reaching cerebrospinal fluid. A pharmacokinetic study in rats determined that phenazopyridine metabolites were present in high levels in the kidney and liver. Read more
This drug is rapidly excreted by the kidneys, up to 65% of a dose administered orally may be excrete... This drug is rapidly excreted by the kidneys, up to 65% of a dose administered orally may be excreted as unchanged drug in the urine. The clearance of phenazopyridine may be decreased with impaired renal or hepatic function and is contraindicated in these conditions. Read more
The mean elimination half-life of phenazopyridine is 7.35 hours in rats with healthy renal function.... The mean elimination half-life of phenazopyridine is 7.35 hours in rats with healthy renal function. The half-life in man is not readily vailable in the literature. Read more
Route of elimination
Up to 65% of an oral phenazopyridine dose is quickly excreted by the kidneys as unchanged drug measu...
Up to 65% of an oral phenazopyridine dose is quickly excreted by the kidneys as unchanged drug measured in the urine.
The pharmacokinetics of this drug have not been evaluated in depth in man. In a small group of healthy research volunteers, 90% of a daily 600 mg oral dose of phenazopyridine hydrochloride was found to be excreted within 1 day, with 41% as unchanged drug and 49% as phenazopyridine metabolites. Another study in humans determined that 80.07 ± 4.54 percent of the dose was cleared in the urine within 48 hours of administration. In rats, biliary excretion was high, with 40.7% of a dose excreted in 8 hours. Read more
The oral LD50 of phenazopyridine in rats is 472 mg/kg.[
The oral LD50 of phenazopyridine in rats is 472 mg/kg.
Administering excess phenazopyridine above the daily recommended dose in those with healthy or impaired kidney function may increase the drug concentration and predispose the patient to toxicity. When a large overdose occurs, methemoglobinemia results.[5,6] To treat this condition, Methylene blue at 1 to 2 mg/kg/dose should be administered intravenously as a 1% solution as deemed necessary. Its administration is likely to cause a rapid reduction of the methemoglobinemia state and relieve the associated cyanosis. Hemolytic anemia is also a risk when an overdose occurs, and “bite cells” may be observed in a blood smear after an overdose with phenazopyridine. Red blood cell G6PD deficiency may increase the risk of hemolysis, and even normal doses can lead to methemoglobinemia in patients with this condition. Nephrotoxicity, renal failure, and hepatic impairment may also occur in a case of overdose with this drug. Administer symptomatic and supportive treatment as necessary.[4,7,18] Read more
|Effect||Regions||Age Groups||Incidences||Evidence Type|
|Reversible loss of colour vision||Canada||
|Discoloration of Body Fluids||US||
- Take with food to reduce irritation.
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- 6 . Murphy T, Fernandez M: Acquired methemoglobinemia from phenazopyridine use. Int J Emerg Med. 2018 Nov 12;11(1):45. doi: 10.1186/s12245-018-0208-5. [PubMed: 31179913]
- 7 . Chang LC, Kuo CW, Chau T, Lin SH: Phenazopyridine-induced hemolytic anemia in advanced kidney disease. J Am Geriatr Soc. 2014 Dec;62(12):2464-6. doi: 10.1111/jgs.13161. [PubMed: 25516057]
- 8 . Aizawa N, Wyndaele JJ: Effects of phenazopyridine on rat bladder primary afferent activity, and comparison with lidocaine and acetaminophen. Neurourol Urodyn. 2010 Nov;29(8):1445-50. doi: 10.1002/nau.20886. [PubMed: 20976818]
- 9 . Thomas BH, Whitehouse LW, Solomonraj G, Paul CJ: Excretion of phenazopyridine and its metabolites in the urine of humans, rats, mice, and guinea pigs. J Pharm Sci. 1990 Apr;79(4):321-5. doi: 10.1002/jps.2600790410. [PubMed: 2352143]
- 10 . Johnson WJ, Chartrand A: The metabolism and excretion of phenazopyridine hydrochloride in animals and man. Toxicol Appl Pharmacol. 1976 Aug;37(2):371-6. doi: 10.1016/0041-008x(76)90100-9. [PubMed: 982458]
- 11 . Li KJ, Chen QH, Zhang Z, Zhou P, Li P, Liu J, Zhu J: Determination of phenazopyridine in human plasma by GC-MS and its pharmacokinetics. J Chromatogr Sci. 2008 Sep;46(8):686-9. doi: 10.1093/chromsci/46.8.686. [PubMed: 18796223]
- 12 . Thomas BH, Whitehouse LW, Solomonraj G, Paul CJ: Metabolism and disposition of phenazopyridine in rat. Xenobiotica. 1993 Feb;23(2):99-105. [PubMed: 8498084]
- 13 . Pitre D, Maffei-Facino R: Isolation and identification of two hydroxylated metabolites of phenazopyridine in rat urine. Farmaco Sci. 1977 Jun;32(6):453-60. [PubMed: 872925]
- 14 . Phenazopyridine Hydrochloride [Link]
- 15 . Drug summary: phenazopyridine [Link]
- 16 . FDA information Phenazopyridine [Link]
- 17 . HMDB, phenazopyridine [Link]
- 18 . Phenazopyridine DailyMed [Link]
- 19 . MSDS, Phenazopyridine [Link]
- 20 . UPMC: Final Diagnosis -- Suicide Attempt with Ingestion of Pyridium Tablets [Link]
- 21 . Intracellular Drug Bioavailability: Effect of Neutral Lipids and Phospholipids [Link]
- 22 . O Factors Affecting Drug Metabolism [Link]
- 23 . Phenazopyridine hydrochloride [Link]