A 45-year-old woman on nitrofurantoin 100 mg MR capsules twice daily for a 3-day course reports that her urine has turned dark yellow-brown. What is the most appropriate response?

• A. Explain that urine discolouration is a harmless and expected side effect of nitrofurantoin
• B. Advise stopping the medication and seeking a renal function test
• C. Suggest that she may have a urinary tract infection requiring different treatment
• D. Recommend increasing fluid intake and monitoring for other symptoms

Answer: (A)

Discolouration of urine with nitrofurantoin is a known, harmless effect. The drug and its metabolites can color urine a dark yellow-brown as they are excreted, so this change does not indicate kidney damage or the need to stop treatment. The best approach is to reassure the patient and continue the prescribed course. A renal function test isn’t required solely due to this urine colour change. Encouraging general hydration is fine, but it won’t change the need to continue therapy. If other symptoms appear—such as fever, severe nausea, vomiting, rash, shortness of breath, or signs of liver or lung toxicity—seek medical advice promptly.