Penicillin Flashcards
MOA of penicillin?
bactericidal– inhibits the with the last step of synthesis of cell wall by three ways
Penicillin binding Proteins
inhibition of transpeptidation reaction(inhibibtion of cross linkage)
Production of autolysin
Where are PBP located?
bacterial cytoplasmic memberane
why is staph resistant to methicillin
due to alterations in PBP
how does production of autolysin effect the bacterial cell?
Many bacteria, particularly the grampositive
cocci, produce degradative enzymes (autolysins) that
participate in the normal remodeling of the bacterial cell wall. In
the presence of a penicillin, the degradative action of the autolysins
proceeds in the absence of cell wall synthesis. Thus, the
antibacterial effect of a penicillin is the result of both inhibition
of cell wall synthesis and destruction of the existing cell wall by
autolysins.
how are penicillins excreted out of the body?
excreted by kidney (excreted unchanged in urine)
what is the mechanism of excretion of penicillins through kidney?
Active tubular Excretion
the excretion of penicllin is effected by which drug?
probenecid(causes inhibition of active tubular excretion)
the excretion of penicllins is effected by which drug?
probenecid(causes inhibition of active tubular excretion)
what is the only penicllin that is excreted by a route other than kidney
Nafcillin (excreted by a biliary route)
absorption of penicillin after oral administration
incompletely absorbed (amoxicillin is completely absorbed)
antibacterial spectrum of penicillins
G+ve: → cell wall is easily penetrated.
G-ve: → envelope around cell wall, however porins permit entrance of penicillins.
which microorganism lacks porins that makes it very resistant to penicillin action?
pseudomonas aeruginosa
Penicillins in “Natural pencillins”?
Penicllin G
Penicillin V
Which is more acid stable G or V
V
which gram + cocci is natural penicillin active against?
Streptococcus(Pneumonia, pyrogenes, viridans)
which gram - cocci is natural penicillin active against?
neisseria (gonorrhea, meningitides)
is natural penicillin active against spirochetes?
treponema palladium(syphilis)
which anerobic is natural penicillin active against?
clsostridium pefringens
which gram + bacilli is natural penicillin active against?
corynebacterium diptheria
bacillus anthracis
the class Anti Staphylococcal penicllins include which antibiotics?
Methicillin
Oxacillin
Nafcillin
Dicloxacillin
MOND
Are antistaphylococcal penicillins (MOND) resistant to penicillanase (Beta lactamase)?
Yes
what toxicity does methicillin cause?
interstitial nephritis
What is MRSA and its treatment?
Methicillin resistant Staph Aureus
treated with vancomycin
antibiotics in Extended spectrum
Ampicillin and amoxicillin
spectrum of extended spectrum antibiotics?
same as penicillin g but with more effect on gram- bacilli( H influenza, E coli)
drug of choice in listeria monocytogenes(Gram +)
Amoxicillin
which drug is used as a prophylactic agent to prevent bacterial endocarditis
Amoxicillin
what is done to extended spec antibiotics to inc their activity against Beta lactamase producing organisms
sulbactam and clavulanic acid
what drug are included in antipseudomonal penicillins?
(Carbenicillin, Piperacillin, Ticarcillin) [CPT]
which organism do (Carbenicillin, Piperacillin, Ticarcillin) [CPT] acts on
pseudomonas aeruginosa
to enhance the activity of piperacillin what is it combined with
Tazobactam
to enhance the activity of ticarcillin what is it combined with
clavulinic ACID
Penicillins + Aminoglycosides
Synergistic effect as penicillins inhibit cell wall synthesis & A.G. inhibits protein synthesis with enhanced permeability.
*Caution: penicillin + A.G not in the same vial as: → (+ve) A.G. + (-ve) penicillin→ ppt
Routes of administration:*
*CPT & their combination
IV & IM
Route of administration
Penicillin V, Amoxicillin & Ampicillin +Clavulonic acid
oral
Route of administration
Procaine penicillin G& benzathine penicillin G
depot IM slowly absorbed into the circulation
route of administraion
*MOND→
given before food(30-60 min)
adverse effects of penicillins
Hypersensitivity → most common.
The metabolite penicilloic acid reacts with proteins→ Hapten that causes immune Rx.
2) Diarrhea→ pseudomembranous colitis.
3) Nephritis→ mainly Methicillin.
4) Neurotoxicity→ epileptic patients at risk.
5) Hematologic toxicities→ ↓ coagulation (CPT).
6) Cation toxicity: penicillins are administered as Na+ or K+ salt.
*Test of penicillins Hypersensitivity:
Penicilloyl- polylysine skin test
ticarcillin causes what as a disodium salt
inc risk of HTN
also has an antiplatelet effect
why is ticarcillin preferred over carbenicillin in pts with CHF
Because dose of Ticarcillin is 1/2 that of Carbenicillin.
patient with penicillin allergy don’t shift to cephalosporin but shift to
erythromycin
cross hypersensitivity risk bw penicillin and cephalosporin
10%
