<prompt> All of the following statement about penicillin G are true except -It is actively secreted in tubulesIt is never administered orallyIt is effective against gram positive as well as gram negative bacteriaIt acts by inhibiting cell wall synthesis  <response>: Ans. is b i.e., It is never administered orally o Here comes the confusing one. o In this question there is confusion between option b and c. o First see option b Penicillin G is degraded by acid. So, most of the time it is given by injection. But oral preparations are also available Despite the convenience of oral administration of penicillin G, this route should be used only in infections in which clinical experience has proven its efficacy. -Goodman Gilman So, option b is absolutely wrong and is the answer of our question. o Now see option C Penicillin G is a narrow spectrum penicillin, i.e. activity is limited primarily to gram positive bacteria but it has activity against some gram negative organisms also, e.g. meningococci, gonococci if strains are sensitive, few strains of E.coli. So, option C is paially correct. About other options o Penicillin is primarily excreted by kidney -- 10-20 by glomerular filtration and 80-90 by active tubular secretion -- Active secretionis inhibited by probenacid which increases blood concentration of penicillin. o Penicillin acts by inhibiting cell wall synthesis. Also know o Penicillin G benzyl penicillin has a sho VA. So, it has to be given 6-12 hourly. o Procaine penicillin and benzathine penicillin longest acting are long acting due to slow release. o Extended broad spectrum penicillins Aminopenicillins, Carboxypenicillins and ureidopenicillins are active against gram negative organisms as well in addition to gram positive oraganisms, though their activity against gram positive organisms is less than penicillin G. o Activity of penicillins against gram positive organisms -- Penicillin G max Extendend spectrum penicilins b- lactamase resistant penicillins methicillin others. 