Final answer:
Rifampin, a drug used to treat tuberculosis, causes a side effect where a patient's body fluids may turn red-orange. This effect is harmless and does not denote any harm to the patient.
Step-by-step explanation:
The side effect of a tuberculosis treatment drug that causes red-orange body fluids is attributed to the drug rifampin. Rifampin is commonly used in combination with other medications, such as isoniazid, to treat tuberculosis (TB). When a patient takes rifampin, it can lead to the discoloration of body fluids, including urine, sweat, tears, and saliva, turning them a red-orange hue. This side effect is usually harmless but can be alarming to the patient if they are not warned beforehand. It is essential to be aware of this effect to avoid confusion or concern. On the other hand, the drug isoniazid, which is also used to treat TB, can lead to other side effects such as hepatotoxicity, neurotoxicity, and hematologic toxicity, but it does not cause the red-orange discoloration of body fluids.