A nurse is caring for a client who has active pulmonary tuberculosis (TB) and a new prescription for rifampin (Rifadin). The nurse should instruct the client that they should expect which of the following clinical manifestations while taking this medication?

A) Black-colored stools: Black-colored stools are often a sign of gastrointestinal bleeding, particularly if the stool has a tarry appearance. This is not a common or expected side effect of rifampin. While rifampin can cause a variety of side effects, black stools are more commonly associated with gastrointestinal conditions or medications that irritate the stomach or gastrointestinal tract, such as iron supplements or nonsteroidal anti-inflammatory drugs (NSAIDs). Therefore, black stools should be investigated further and are not a typical reaction to rifampin. B) Orange-colored secretions: Rifampin is known to cause a harmless but notable side effect: the discoloration of bodily fluids, including urine, sweat, saliva, and tears, turning them a bright orange or red color. This is a well-known effect of the drug and is typically harmless, although it can be alarming for the patient. Patients should be instructed about this effect, especially for things like wearing contact lenses (which can be stained) and avoiding staining clothes. This is the most appropriate and expected clinical manifestation to inform the patient about. C) Staining of teeth: Staining of teeth is not a common side effect of rifampin. Although some antibiotics, such as tetracyclines, are associated with tooth discoloration (especially in children), rifampin is not known to cause staining of the teeth. This side effect is not typically seen in patients taking rifampin for tuberculosis or other infections. D) Constipation: Constipation is not a typical or common side effect of rifampin. While gastrointestinal side effects like nausea, vomiting, and abdominal discomfort can occur, constipation is not one of the expected reactions. Rifampin is more likely to cause digestive upset rather than constipation. If constipation occurs, it is more likely related to other factors such as diet, hydration, or other medications, rather than being directly caused by rifampin.