Which medication is known to cause orange-red discoloration of body fluids?

Rifampin is well-known for causing orange-red discoloration of body fluids, including urine, sweat, saliva, and tears. This effect occurs because rifampin is a potent dye that can change the color of secretions due to its chemical structure. The discoloration is generally harmless and is a result of the compound being excreted from the body. This characteristic can be a point of concern for patients who may be alarmed by the change in color, but it does not indicate an adverse reaction or toxicity.

In contrast, the other medications listed do not typically result in such discoloration of body fluids. Penicillin, for example, does not have this side effect and is responsible for different types of allergic reactions in some cases. Tetracycline, while it has its own range of side effects, is not known for causing changes in the color of bodily fluids. Cephalexin, a cephalosporin antibiotic, similarly does not cause discoloration and is focused more on treating bacterial infections through its action rather than having noticeable effects on body fluids.