Which of the following drugs does not affect DNA synthesis?
(A) Rifampicin (B) Linezolid (C) Nitrofurantoin (D) Metronidazole
(B) Ans: B. Linezolid(Ref Goodman Gilman I3/e p796, 12/e p1537; Katzung 12/e p817; KDT 7/e p758, 817, 6/e p669)Linezolid inhibits protein synthesis by binding to the P site of the 50S ribosomal subunit and preventing formation of the larger ribosomal-fMet-tRNA complex that initiates protein synthesis.Nitrofurantoin - Works by damaging bacterial DNA.Metronidazole - Forms toxic free radical metabolites in the bacterial cell that damage DNA.Rifampicin - Inhibit DNA-dependent RNA polymerase.