Medications that can turn urine orange Isoniazid, an antibiotic used for the treatment of tuberculosis Sulfasalazine, an anti-inflammatory used to treat rheumatoid arthritis and ulcerative colitis Riboflavin (also known as vitamin B2), a vitamin included in many over-the-counter multivitamins   Medications that can turn urine brown Metronidazole (Flagyl), an antibiotic used to treat bacterial vaginosis, C. diff diarrhea and