This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
A middle-aged man with chronic renal failure is diagnosed to have sputum-positive pulmonary tuberculosis. His creatinine clearance is 25 ml/min. All of the following drugs need modification in doses EXCEPT : 
Select and explain. 
A. Isoniazid, B. Streptomycin, C. Rifampicin, D. Ethambutol
C: Rifampicin
Answer: C: Rifampicin 
Explanation: Rifampicin is secreted in bite, so it does not require dose adjustment in renal failure.