<prompt> All of the following statements about penicillin G are true EXCEPT :It is actively secreted in tubulesIt is never administered orallyIt is effective, against gram positive as well as some gram negative bacteriaIt acts by inhibiting cell wall synthesis  <response>: Penicillin act by inhibiting bacterial cell wall synthesis via the inhibition of transpeptidation reaction.Penicillin G is the drug of choice for:- Gram ve bacteria like Streptococcus, Pneumococcus, non-beta-lactamase producing Staphylococcus, Clostridium and other gram-positive rods- Gram-negative bacteria like Meningococci, Enterococci and non-β-lactamase producing gram-negative anaerobic bacteria- Actinomycetes and Treponema pallidum syphilisPenicillin is rapidly excreted by the kidney. 90 excretion is by tubular secretion whereas 10 is by glomerular filtration. Probenecid competes with tubular secretion and prolongs the duration of action.Penicillin G is less effective by oral route due to destruction by hydrochloric acid in the stomach. Penicillin V is acid stable and thus can be given orally. Mostly penicillin G is administered parenterally i.m. or i.v. but it can be administered orally for mild infections. Katzung Pg. 742, in preparations available, also shows the oral and parenteral preparations.Thus penicillin is never administered orally is not a true statement because it can be used orally but commonly used parenterally. 