All of the following statement about penicillin G are true except -
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 secretion'is 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).
It is actively secreted in tubules
It is never administered orally
It is effective against gram positive as well as gram negative bacteria
It acts by inhibiting cell wall synthesis