A patient taking INH, rifampin, and pyrazinamide reports red urine. Which drug is most likely responsible?

A patient taking INH, rifampin, and pyrazinamide reports red urine. Which drug is most likely responsible?

• A. Isoniazid
• B. Pyrazinamide
• C. Rifampin
• D. Ethambutol

Answer: (C)

Rifampin is the drug most likely responsible. It commonly causes discoloration of bodily fluids, especially turning urine, tears, and sweat an orange-red color. This happens because rifampin and its metabolites are excreted through the kidneys and secretions, giving these fluids a characteristic hue. Patients often notice it as a harmless, though sometimes alarming, change and may even find that it stains clothing or contact lenses. Understanding the other drugs helps reinforce why this fits here. Isoniazid is more associated with hepatotoxicity and peripheral neuropathy due to vitamin B6 depletion, not urine color changes. Pyrazinamide can raise uric acid levels and cause gout-like symptoms, but it doesn’t typically color urine. Ethambutol is known for optic neuritis and visual changes, not urine color changes. So, the red-orange urine points to rifampin, since this is a hallmark adverse effect of that specific drug in the regimen. If the patient hasn’t already been warned, you can reassure them that while the color change is benign, they should report any other symptoms or signs of toxicity.

Rifampin is the drug most likely responsible. It commonly causes discoloration of bodily fluids, especially turning urine, tears, and sweat an orange-red color. This happens because rifampin and its metabolites are excreted through the kidneys and secretions, giving these fluids a characteristic hue. Patients often notice it as a harmless, though sometimes alarming, change and may even find that it stains clothing or contact lenses.

Understanding the other drugs helps reinforce why this fits here. Isoniazid is more associated with hepatotoxicity and peripheral neuropathy due to vitamin B6 depletion, not urine color changes. Pyrazinamide can raise uric acid levels and cause gout-like symptoms, but it doesn’t typically color urine. Ethambutol is known for optic neuritis and visual changes, not urine color changes.

So, the red-orange urine points to rifampin, since this is a hallmark adverse effect of that specific drug in the regimen. If the patient hasn’t already been warned, you can reassure them that while the color change is benign, they should report any other symptoms or signs of toxicity.