Phenazopyridine

How it works

It exerts a local anaesthetic or analgesic action on the urinary tract mucosa, though the precise mechanism is not fully understood; it is excreted in the urine where it acts directly.

Prescribing in practice

• Provides only symptomatic relief and does not treat infection, so it must not replace appropriate antimicrobial therapy where a urinary tract infection is present.
• Use is contraindicated in significant renal impairment, as accumulation increases the risk of toxicity.
• It should be used only for a short course; prolonged use raises the risk of methaemoglobinaemia and haemolytic anaemia, particularly in glucose-6-phosphate dehydrogenase deficiency.

Monitoring

Monitor for symptom resolution and watch for signs of methaemoglobinaemia or haemolysis (cyanosis, breathlessness) especially with renal impairment or prolonged use.

Counselling the patient

• Warn that it turns urine an orange or red colour, which is harmless but can stain clothing and contact lenses.
• Advise stopping the drug and seeking review if the skin or eyes appear yellow or if breathlessness develops.
• Explain it relieves symptoms only and any prescribed antibiotic must still be completed.

Evidence & guidelines

It is an established symptomatic urinary analgesic; refer to the SPC and current prescribing references for licensed indications and cautions.