Rifampin is the Cause of Orange Discoloration
Rifampin is definitively responsible for the orange coloration of urine and saliva in this patient. This is a well-known, harmless side effect that occurs predictably with rifampin therapy and serves as a useful marker of medication adherence 1, 2.
Mechanism and Clinical Presentation
- Rifampin causes characteristic orange-red discoloration of body fluids including urine, saliva, sweat, tears, and sputum through direct excretion of the drug and its metabolites 2.
- This discoloration is completely benign and expected, occurring in essentially all patients taking rifampin 1.
- The FDA drug label explicitly warns patients that rifampin "may produce a discoloration (yellow, orange, red, brown) of the teeth, urine, sweat, sputum, and tears" 2.
Why Not the Other Medications?
- Ethambutol does not cause body fluid discoloration; its primary concern is optic neuritis affecting vision 1.
- Isoniazid does not discolor body fluids; its main adverse effects include hepatotoxicity and peripheral neuropathy 1.
- Moxifloxacin (a fluoroquinolone) does not cause orange discoloration of body fluids 3.
- Pyrazinamide does not discolor body fluids; it primarily causes hepatotoxicity, hyperuricemia, and arthralgia 4.
Clinical Utility of This Side Effect
- The orange/pink coloration of urine provides a practical method to verify patient compliance with rifampin-containing regimens 1.
- Healthcare providers can assess urine visually or through laboratory testing to confirm medication adherence 1.
- Patients must be counseled about this expected side effect before starting therapy to prevent unnecessary alarm 2.
Important Patient Counseling Points
- Soft contact lenses may be permanently stained by the discolored tears, so patients should be warned to avoid wearing them during rifampin therapy 2.
- The discoloration is not a sign of toxicity or harm and does not require any intervention 1.
- Patients should be reassured that this effect will resolve after completing rifampin therapy 2.