FENAZOPIRIDINA

FENAZOPIRIDINA EN VADEMECUM

DESCRIPCION

La fenazopiridina es un analgésico oral específico para el tracto urinario. Se utiliza para el alivio sintomático del ardor, urgencia, frcuencia y otros síntomas molestos que resultan de la irritación de la mucosa del tracto urinario inferior. La fenazopiridina es un colorante azo que se excreta en la orina que resulta así coloreada en anaranjado-rojizo.

Mecanismo de acción: no se conoce el mecanismo de acción de la fenazopiridina. Solo se sabe que se excreta en la orina y que ocasiona un efecto anestésico sobre la mucosa del tracto urinario

Farmacocinética: la fenazopiridina se administra por vía oral. No se conoce la farmacocinética de esta fármaco. Se cree que unas pequeñas cantidades del fármaco atraviesan la barrera placentaria y pueden entrar en el sistema nervios central. El fármaco es rápidamente excretado por los riñones con el 65% de la dosis del fármaco sin alterar.

INDICACIONES Y POSOLOGIA

Tratamiento sintomático de la disuria, urgencias y molestias devidas a la irritación de la mucosa intestinal causada por un trauma, cirugía, procedimientos endoscópicos, etc

Oral dosage: Adults: 200 mg PO three times per day. Phenazopyridine therapy should not exceed 2 days when used concomitantly with an antibacterial agent. Children†: 4 mg/kg PO three times per day. Phenazopyridine therapy should not exceed 2 days when used concomitantly with an antibacterial agent. Patients with renal impairment: Dosage adjustment is recommended; however, specific guidelines are not available. †non-FDA-approved indication

Oral Administration •Phenazopyridine is administered orally. Administer with food or after meals to minimize GI discomfort. •Extemporaneous preparation: To prepare a 10 mg/ml suspension, crush three 200 mg tablets and mix with a small amount of distilled water or glycerin. Then, add 20 ml of Cologel® and levigate until a uniform mixture is obtained. Add sufficient 2:1 simple syrup/cherry syrup mixture to make a final volume of 60 ml. Store in an amber container. Shake well before using. Preparation is stable for 60 days under refrigeration.

CONTRAINDICACIONES

 

The use of phenazopyridine for relief of urinary symptoms should not delay the definitive diagnosis and treatment of causative conditions. Because phenazopyridine only provides symptomatic relief, appropriate treatment of the cause of pain must be initiated and phenazopyridine should be discontinued when symptoms are controlled. Phenazopyridine should not be used for more than 2 days in a patient being treated for a urinary tract infection. There is no evidence that the combined administration of phenazopyridine and an antibacterial provides greater benefit than administration of the antibacterial alone after 2 days. Phenazopyridine is contraindicated in patients with renal impairment, renal disease (e.g., glomerulonephritis), uremia, or hepatic disease (including hepatitis). A yellowish tinge of the skin or sclera may indicate accumulation of the drug due to impaired renal excretion. Because renal function may decline with advancing age, phenazopyridine should be used with caution in the elderly. Use of phenazopyridine can cause hemolytic anemia. Because red blood cell G6PD deficiency may predispose to hemolysis, phenazopyridine should not be used in this patient population. Phenzopyridine is an azo dye. Irreversible staining of soft contact lenses has been reported. Therefore, patients should not wear soft contact lenses while taking this medication. Phenazopyridine produces an orange to red color in the urine and may stain fabric. Stains on clothing may be removed with a 0.25% solution of sodium dithionate or sodium hydrosulfite. Phenazopyridine is classified as pregnancy category B. There are no adequate and well controlled studies in pregnant women. However, reproduction studies in rats at doses up to 50 mg/kg/day have revealed no evidence of impaired fertility or harm to the fetus. Nevertheless, phenazopyridine should be used during pregnancy only if clearly needed. It is not known if phenazopyridine is excreted in human milk. Thus, phenazopyridine should be used with caution in a woman who is breast-feeding. Because phenazopyridine is an azo dye, the drug may interfere with urinalysis based on spectrometry or color reactions. Laboratory tests which may be affected include: phenolsulfonphthalein excretion test, urinary glucose tests (e.g., Clinistix®, Tes-Tape®) urinary ketone tests using sodium nitroprusside (Acetest®, Ketostix®) or Gerhardt ferric chloride, urinary protein tests, urinary urobilinogen determinations, and screening tests and assays for porphyrins.

INTERACCIONES

No se han descrito interacciones clínicamente significativas con este fármaco

REACCIONES ADVERSAS

Se han comunicado metahemoglobinemia y anemia hemolytica con el uso de la fenazopiridina, generalmente después de una sobredosis, aunque estas reacciones adversas han sido también observadas con dosis terapéuticas en pacientes con insuficiencia renal. La metahemoglobinemia se debe a productos que oxidan el hierro de la hemoglobina desde su estado de oxidación ferroso a férrico. La oxidación concomitantre de la globina (proteína de la hemoglobina) induce la precipitación de los cuerpos de Heinz y la anemia hemolítica

anemia have been reported with use of phenazopyridine,[1803] usually following an overdose. However, these adverse events have also been reported with usual therapeutic dosages in the setting of renal impairment or end stage renal disease.[1804] Methemoglobinemia results from exposure to chemicals that oxidize the iron in hemoglobin from its ferrous to its ferric state. Concomitant oxidation of hemoglobin protein may cause its precipitation (as Heinz bodies) and a hemolytic anemia (with bite cells seen on peripheral blood smear). If a patient develops methemoglobinemia, methylene blue should be administered intravenously. Although the manufacturer recommends oral ascorbic acid as an alternative to methylene blue, ascorbic acid reduces methemoglobinemia at a slower rate and is therefore less effective. Acute renal failure (e.g., renal tubular necrosis) may occur rarely with use of phenazopyridine. Patients with preexisting renal disease may be predisposed to the development of renal failure. A few cases of hepatotoxicity also have been reported. A dose-related toxic hepatitis has been observed, as well as a hypersensitivity-mediated hepatitis associated with elevated hepatic enzymes, jaundice, fever and eosinophilia. Aseptic meningitis has been reported in one patient treated with phenazopyridine; a causal relationship was verified upon rechallenge. Phenazopyridine is an azo dye and can discolor many bodily fluids. It can cause contact lens discoloration and, because it is excreted in the urine, can cause urine discoloration. Other adverse reactions reported with use of phenazopyridine include headache, maculopapular rash, pruritus, anaphylactoid reactions, nausea/vomiting, and gastrointestinal disturbances.

 

I
 

Phenazopyridine Pyridiate®, Pyridium®, Urodol®, Urogesic®, Viridium® | Azo-Standard® | Urodine®

 

 
 

REFERENCIAS

  • Noonan HM, Kimbrell M, Johnson WB, et al. Phenazopyridine-induced hemolytic anemia. Urology 1983;21:623—4.
  • Fincher ME, Campbell HT. Methemoglobinemia and hemolytic anemia after phenazopyridine hydrochloride (Pyridium) administration in end-stage renal disease. S Med J 1989;82:372—4.