Phenazopyridine is a chemical which, when excreted into the urine

Urine

Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...

, has a local analgesic

Analgesic

An analgesic is any member of the group of drugs used to relieve pain . The word analgesic derives from Greek an- and algos ....

 effect. It is often used to alleviate the pain

Pain

Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...

, irritation

Irritation

Irritation or exacerbation, in biology and physiology, is a state of inflammation or painful reaction to allergy or cell-lining damage. A stimulus or agent which induces the state of irritation is an irritant...

, discomfort, or urgency

Urinary urgency

Urinary urgency is a sudden, compelling urge to urinate. It is often, though not necessarily, associated with urinary incontinence, polyuria, nocturia, and interstitial cystitis. It tends to increase with age...

 caused by urinary tract infections, surgery

Surgery

Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...

, or injury to the urinary tract. Phenazopyridine was discovered by Bernhard Joos

Bernhard Joos

Bernhard Joos , was the son of Dr. Bernhard Joos and Olga Sturzenegger....

, the founder of Cilag

Cilag

Cilag AG is a Swiss pharmaceutical company. Cilag is a subsidiary of American pharmaceutical giant Johnson & Johnson. The company's global marketing activities are operated by Janssen-Cilag, a merger with another Johnson & Johnson subsidiary, Janssen Pharmaceutica.-Company history:In 1933, Swiss...

.

Medical uses

Phenazopyridine is prescribed for its local analgesic effects on the urinary tract. It is typically used in conjunction with an antibiotic when treating a urinary tract infection. Phenazopyridine is not an antibiotic, but used in conjunction with an antibiotic can speed the early period of recovery from such an infection. In this combination, phenazopyridine is taken for only a short time, typically two days, while the antibiotic is continued for longer. After two days, there is little evidence of any benefit from continued administration of phenazopyridine versus administration of an antibiotic only.

Phenazopyridine is also prescribed for other cases to relieve irritation or discomfort during urination. For example, it is often prescribed after the use of a catheter

Catheter

In medicine, a catheter is a tube that can be inserted into a body cavity, duct, or vessel. Catheters thereby allow drainage, administration of fluids or gases, or access by surgical instruments. The process of inserting a catheter is catheterization...

 or after penile surgery which results in the irritation of the lining of the urinary tract.

The American Urological Association has recommended the use of phenazopyridine as a first stage treatment for interstitial cystitis

Interstitial cystitis

Interstitial cystitis or bladder pain syndrome is a chronic, oftentimes severely debilitating disease of the urinary bladder...

.

Pharmacokinetics

The drug is administered as a tablet, in either 100 mg or 200 mg doses of phenazopyridine hydrochloride

Hydrochloride

In chemistry, hydrochlorides are salts resulting, or regarded as resulting, from the reaction of hydrochloric acid with an organic base . This is also known as muriate, derived from hydrochloric acid's other name: muriatic acid....

. The tablets have a light red, dark red or dark violet color, and are taken with food.

The full pharmacokinetic properties of phenazopyridine have not been determined. It has mostly been studied in animal model

Animal model

An animal model is a living, non-human animal used during the research and investigation of human disease, for the purpose of better understanding the disease without the added risk of causing harm to an actual human being during the process...

s, but they may not be very representative of humans. Rat models have shown its half-life to be 7.35 hours, and that it is excreted 40% hepatically.

Its mode 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

Hydroxylation

Hydroxylation is a chemical process that introduces a hydroxyl group into an organic compound. In biochemistry, hydroxylation reactions are often facilitated by enzymes called hydroxylases. Hydroxylation is the first step in the oxidative degradation of organic compounds in air...

 is the major form of metabolism in humans, and the azo

Azo

Azo may refer to:* Azo compound, chemistry functional group and class of compounds, also used for CDs and DVDs* A urinary tract analgesic also known as phenazopyridine* the medieval Italian jurist, see Azo of Bologna...

 bond is usually not cleaved. On the order of 65% of an oral dose will be excreted directly into the urine chemically unchanged.

Side effects

Phenazopyridine frequently causes a distinct color change in the 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 drug in the body. Users of phenazopyridine are warned not to wear contact lenses, as phenazopyridine has been known to permanently discolor contact lenses and fabrics.

Phenazopyridine can also cause headache

Headache

A headache or cephalalgia is pain anywhere in the region of the head or neck. It can be a symptom of a number of different conditions of the head and neck. The brain tissue itself is not sensitive to pain because it lacks pain receptors. Rather, the pain is caused by disturbance of the...

s, upset stomach (especially when not taken with food), or dizziness

Dizziness

Dizziness refers to an impairment in spatial perception and stability. The term is somewhat imprecise. It can be used to mean vertigo, presyncope, disequilibrium, or a non-specific feeling such as giddiness or foolishness....

. Less frequently it can cause a pigment change in the skin or eyes, to a noticeable yellowish color. This is due to a depressed excretion via the kidneys causing a build up of the drug in the skin, and normally indicates a need to discontinue usage. Other such side effects include fever

Fever

Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...

, confusion

ConFusion

ConFusion is an annual science fiction convention organized by the Stilyagi Air Corps and its parent organization, the Ann Arbor Science Fiction Association. Commonly, it is held the third weekend of January. It is the oldest science fiction convention in Michigan, a regional, general SF con...

, shortness of breath, skin

Skin

-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...

 rash

Rash

A rash is a change of the skin which affects its color, appearance or texture. A rash may be localized in one part of the body, or affect all the skin. Rashes may cause the skin to change color, itch, become warm, bumpy, chapped, dry, cracked or blistered, swell and may be painful. The causes, and...

, and swelling

Swelling (medical)

In medical parlance, swelling is the transient enlargement or protuberance in the body and may include tumors. According to cause, it may be congenital, traumatic, inflammatory, neoplastic or miscellaneous....

 of the face, fingers, feet, or legs. Long-term use may cause yellowing of nails.

Phenazopyridine should be avoided by people with glucose-6-phosphate dehydrogenase deficiency

Glucose-6-phosphate dehydrogenase deficiency

Glucose-6-phosphate dehydrogenase deficiency is an X-linked recessive hereditary disease characterised by abnormally low levels of glucose-6-phosphate dehydrogenase , a metabolic enzyme involved in the pentose phosphate pathway, especially important in red blood cell metabolism. G6PD deficiency is...

, because it can cause hemolysis

Hemolysis

Hemolysis —from the Greek meaning "blood" and meaning a "loosing", "setting free" or "releasing"—is the rupturing of erythrocytes and the release of their contents into surrounding fluid...

 (destruction of red blood cell

Red blood cell

Red blood cells are the most common type of blood cell and the vertebrate organism's principal means of delivering oxygen to the body tissues via the blood flow through the circulatory system...

s) due to oxidative stress

Oxidative stress

Oxidative stress represents an imbalance between the production and manifestation of reactive oxygen species and a biological system's ability to readily detoxify the reactive intermediates or to repair the resulting damage...

. It has been reported to cause methemoglobinemia

Methemoglobinemia

Methemoglobinemia is a disorder characterized by the presence of a higher than normal level of methemoglobin in the blood. Methemoglobin is an oxidized form of hemoglobin that has an increased affinity for oxygen, resulting in a reduced ability to release oxygen to tissues. The oxygen–hemoglobin...

 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

Sulfhemoglobinemia

Sulfhemoglobinemia is a rare condition in which there is excess sulfhemoglobin in the blood. The pigment is a greenish derivative of hemoglobin which cannot be converted back to normal, functional hemoglobin...

.

Phenazopyridine is a type of azo dye. Other azo dyes, which were previously used in textiles, printing, and plastic manufacturing, have been implicated as carcinogenic agents that can cause bladder cancer

Bladder cancer

Bladder cancer is any of several types of malignant growths of the urinary bladder. It is a disease in which abnormal cells multiply without control in the bladder. The bladder is a hollow, muscular organ that stores urine; it is located in the pelvis...

. While phenazopyridine has never been shown to cause cancer in humans, evidence from animal models suggests that it is potentially carcinogenic.

Criticism

Because it does not kill the organisms causing a bladder infection, there is a risk that some patients will take phenazopyridine alone to relieve their symptoms instead of seeking a physician first and starting an appropriate antibiotic. The medicine serves to only mask the pain, and does not kill the infection, possibly allowing a simple bladder infection to become a more serious kidney infection if taken alone.

Since phenazopyridine discolors the urine, it interferes with the standard urine dipstick

Urine test strip

A urine test strip or dipstick is a basic diagnostic instrument used to determine pathological changes in the urine in standard urinalysis. A standard urine test strip may comprise up to 10 different chemical pads or reagents which react when immersed in, and then removed from, a urine sample....

 test done in a physician's office, especially the leukocyte esterase

Leukocyte esterase

Leukocyte esterase is a urine test for the presence of white blood cells and other abnormalities associated with infection.White blood cells in the urine usually indicate a urinary tract infection. The leukocyte esterase test detects esterase, an enzyme released by white blood cells. Positive...

 parameter. If the physician determines that the patient is taking phenazopyridine, he or she will tell the patient to discontinue the drug and return in 2 or 3 days for a standard urine test to determine whether the pain is caused by a bladder/urinary tract infection.

Use of phenazopyridine is generally more appropriate once a diagnosis of bladder infection has been established by a medical provider and an antibiotic has been started to kill the infection.

Some physicians use phenazopyridine to relif symptons of catheter discomfort following gynecologic surgery. Although a recent study investigate this relation and discloses: Phenazopyridine does not improve catheter discomfort following gynecologic surgery
No other eviddence was found in Pubmed at this time (november/2011), that support the use of phenazopyridine in catheter discomfort following gynecologic surgery.

Brand names

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

• Azo-Standard
• Baridium
• Nefrecil
• Phenazodine
• Prodium
• Pyridiate
• Pyridium
• Pyridium Plus
• Sedural
• Uricalm
• Uristat
• Uropyrine
• Urodine
• Urogesic
• utistat(ciprofloxacin 250mg+phenazopyridine 200 mg)

External links

• Information about phenazopyridine from the US National Library of Medicine
• Interstitial Cystitis Association
• American Urological Association