What if a patient took AZO (Phenazopyridine) before a urinalysis?

Effect of Phenazopyridine (AZO) on Urinalysis Results

Phenazopyridine (AZO) will interfere with urinalysis results by producing a reddish-orange discoloration of the urine and may interfere with urinalysis tests based on spectrometry or color reactions. 1

How Phenazopyridine Affects Urinalysis

• Phenazopyridine is an azo dye that produces a characteristic reddish-orange discoloration of the urine which can persist while the medication is being taken 1
• The medication can interfere with urinalysis based on spectrometry or color reactions due to its properties as an azo dye 1
• The color change can affect various dipstick parameters that rely on color changes for interpretation, potentially leading to false results 1
• The medication does not have antibacterial properties, meaning it only treats symptoms but not the underlying infection if one is present 2

Clinical Implications

• Phenazopyridine can mask the true color of urine, which might otherwise provide important diagnostic information 1
• Laboratory tests that depend on color reactions (such as glucose, protein, bilirubin, and urobilinogen tests) may yield inaccurate results 1
• The medication may stain fabrics and even contact lenses, which patients should be warned about 1

Recommendations for Clinical Practice

• If urinalysis is needed, it should ideally be collected before starting phenazopyridine or after the medication has been discontinued and cleared from the system 1
• If urinalysis must be performed while the patient is taking phenazopyridine, inform the laboratory about the medication use so they can account for potential interference 1
• Be aware that a yellowish tinge of the skin or sclera may indicate accumulation of the drug due to impaired renal excretion, which would necessitate discontinuation of therapy 1
• Phenazopyridine should only be used for short-term symptomatic relief (typically 2 days) and not as a substitute for appropriate antibiotic therapy when indicated 3, 4

Important Cautions

• Patients often use phenazopyridine for urinary symptoms without seeking medical attention, which can lead to delayed diagnosis and treatment of underlying conditions 2
• There have been cases of progression from uncomplicated cystitis to pyelonephritis when phenazopyridine was used without appropriate antibiotic therapy 2
• The decline in renal function associated with advanced age should be considered when prescribing this medication, as it may accumulate in patients with impaired renal function 1

Proper Use of Phenazopyridine

• Phenazopyridine is effective for relieving urinary pain, burning, and discomfort associated with urinary tract infections or procedures like cystoscopy 3, 4, 5
• It should be used as an adjunct to appropriate antibiotic therapy for urinary tract infections, not as a standalone treatment 3, 4
• Studies have shown that phenazopyridine can significantly reduce pain intensity within 6-12 hours of administration 3, 4

Remember that while phenazopyridine effectively relieves symptoms, it does not treat the underlying cause of urinary symptoms and may mask important diagnostic information if urinalysis is performed while the patient is taking the medication.