Phenazopyridine

Phenazopyridine is a chemical which, when secreted into the urine, has a specifical local analgesic effect. It is often used to alleviate the pain, irritation, discomfort, or urgency caused by urinary tract infections, surgery, or injury to the urinary tract. Phenazopyridine (Pyridacil) was discovered by Dr. Bernhard Joos, the founder of Cilag.

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

Pharmacokinetics
The drug is administered as a tablet, in either 100mg or 200mg doses of Phenazopyridine Hydrochloride. 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. In particular, 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. On the order of 65% of an oral dose will be secreted directly into the urine chemically unchanged.

Side effects
Dangerous and prohibited for G6PDD patients. 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 headaches, upset stomach (especially when not taken with food), or dizziness. 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, confusion, shortness of breath, skin rash, and swelling of the face, fingers, feet, or legs.

Phenazopyridine can cause drug-induced hemolysis in patients with a glucose-6-phosphate dehydrogenase deficiency because of the oxidative stress this drug inflicts on red blood cells (RBC).

Brand Names
In addition to its generic form, phenazopyridine is distributed under the following brand names:
 * Azo-Standard
 * Baridium
 * Nefrecil
 * Phenazodine
 * Prodium
 * Pyridiate
 * Pyridium
 * Sedural
 * Uricalm
 * Uristat
 * Uropyrine
 * Urodine
 * Urogesic