Antibiotics Flashcards
Penicillin G, V: MOA and resistance
first penacillin. Works by binding penacillin binding proteins to prevent crosslinking of bacterial cell wall (blocks transpeptidases). also activates autolytic enzymes.
resistance from penicillinase in bacteria which leaves the beta lactam ring.
Penicillin G is IV and IM, penicillin V is oral.
Penicillin G and V toxicities and uses
gram positive organisms, treponema pallidum, N. menigitidis, actinomyces.
cause hypersensitivities and hemolytic anemia
Ampicillin, amoxicillin. MOA and resistance
similar drugs, but amoxicillin has better oral availability.
also bind penicillin binding proteins to prevent crosslinking of bacterial wall.
they differ from penicillins in that they have a broader spectrum of action. Still susceptible to penicillinase, though you can combine with clauvulanic acid to protect against beta lactamases.
Ampicillin, amoxicillin: clinical use and toxicity
extended spectrum penicillin: gram positives, but HELPSS more: Hib, enteroccoci and e coli, listeria, proteus, salmonella, shigella.
toxicity: hypersensitivity, pseudomembranous colitis
Oxacillin, nafcillin, dicloxacillin: MOA and resistance
mechanism: it’s a penicillin, so it blocks crosslinking of the bacterial cell wall.
special because it is resistant to beta lactamases (bulky R-group blcoks access of beta-lactamase to the the beta lactam ring).
restance: MRSA has an altered penicillin binding site
oxacillin, nafcillin, dicloxacillin: use and toxicity
narrow-spectrum. Good for S. aureas, but not MRSA (MRSA is resistant because it has an alterned penicillin binding site)
toxicity: hypersensitivity, interstial nephritis
ticarcillin, piperacillin: mechanism and resistance
same as penicillin, but extended spectrum to cover pseudomonas and gram negative rods.
resistance: must use with a beta lactamase inhibitor, since it is susceptible to penicillinase.
What are the beta lactamase inhibitors
CAST: clavulanic acid, sulbactam, tazobactam
Mechanism of the cephalosporins; cidal/static,
these are also beta-lactam-like drugs. they inhibit cell wall synthesis. less susceptible to penicillinases. cidal
What organisms aren’t usually covered by cephalosporins?
LAME: listeria, atypicals like chlamydia/mycoplasma, MRSA, enterococci. only exception is ceftarolin, which covers MRSA.
1st gen cephalosporin: coverage/uses
covers PEcK: proteus, E coli, klebsiella.
used prior to surgery to prevent S. aureus wound infections
2nd generation cephalosporins: coverage/uses
HEN PEcKS: Hib, Enetrobacter, Neisseria, Proteus, E coli, Klebsiella, serratia
3rd generation cephalosporins
used for secrious gram negative infections resistant to other beta lactams. Ceftriazone is used for menigitis and gonorrhea, ceftazidime is used for pseudomonas.
cefepime
4th generation cephalosporin. covers pseudomonas and other gram positive organisms
ceftaroline
broad coverage, including MRSA. does NOT cover pseudomonas
toxicity of cephalosporins
hypersensitivity, vitamin K deficiency. increases the toxicity of aminoglycosides
Azotreonam: mechanism
monobactam resistant to beta lactamases. prevents peptidoglycan cross-linking by binding to pencillin binding protein 3. synergistic with aminoglycosides.
azotreonam use and toxicity
gram negative rods ONLY. for penicillin allergic patients and those w/ renal insufficiency who cannot tolerate aminoglycosides
toxicity: usually nontoxic. no cross-allergenicity with penicillins
carbapenems: mechanism, special considerations
esp. imipenem. broad spectrum beta lactamase resistant carbapenem. always administered with cilastin to decrease inactivation of the drug in the renal tubules.
Carbapenems: use and toxicities
gram positive cocci, gram negative rods, anaerobes. toxicities: can cause GI distress, skin rash, and CNS toxicity/seizures at high levels.
Vancomycin mechanism and resistance.
inhibits cell wall peptidoglycan formation by binding D-ala-D-ala portion of cell wall precursors. bactericidial. resistance develops when the bacteria mutates to D-ala-D-lac
vancomycin use and toxicities
used for gram positive only (MRSA, eneterococci; used orally for C. diff).
toxicity: usually well-tolerated, but nephrotoxicity, ototoxicity, thrombophlebitis (vein inflammation). also causes red man syndrome if administered too quickly.
