This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anti-Tuberculosis, Subject name: Pharmacology
A middle aged old man, with chronic renal failure is diagnosed to have sputum-positive pulmonary tuberculosis. His creatinine clearance is 25ml/min. All of the following drugs need modification in doses except: 
Select and explain. 
A. Isoniazide, B. Streptomycin, C. Rifampicin, D. Ethambutol
C: Rifampicin
Answer: C: Rifampicin 
Explanation: Ans. is 'c' i.e. Rifampicin This question has been repeated several times. Its advised to go through tables in C.M.D.T. and in Harrison mentioned above in Ref.More question related to this topic.Most nephrotoxic cephalosporin - cephaloridine*Most nephrotoxic aminoglycoside - Gentamycin*Least nephrotoxic aminoglycoside - Tobramycin*Only tetracycline safe in Renal failure- Doxycycline*Least nephrotoxic antitubercular - Rifampicin*