Antibiotics

Question 1

Penicillin G, V: MOA and resistance

Answer 1

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.

Question 2

Penicillin G and V toxicities and uses

Answer 2

gram positive organisms, treponema pallidum, N. menigitidis, actinomyces.
cause hypersensitivities and hemolytic anemia

Question 3

Ampicillin, amoxicillin. MOA and resistance

Answer 3

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.

Question 4

Ampicillin, amoxicillin: clinical use and toxicity

Answer 4

extended spectrum penicillin: gram positives, but HELPSS more: Hib, enteroccoci and e coli, listeria, proteus, salmonella, shigella.
toxicity: hypersensitivity, pseudomembranous colitis

Question 5

Oxacillin, nafcillin, dicloxacillin: MOA and resistance

Answer 5

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

Question 6

oxacillin, nafcillin, dicloxacillin: use and toxicity

Answer 6

narrow-spectrum. Good for S. aureas, but not MRSA (MRSA is resistant because it has an alterned penicillin binding site)
toxicity: hypersensitivity, interstial nephritis

Question 7

ticarcillin, piperacillin: mechanism and resistance

Answer 7

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.

Question 8

What are the beta lactamase inhibitors

Answer 8

CAST: clavulanic acid, sulbactam, tazobactam

Question 9

Mechanism of the cephalosporins; cidal/static,

Answer 9

these are also beta-lactam-like drugs. they inhibit cell wall synthesis. less susceptible to penicillinases. cidal

Question 10

What organisms aren’t usually covered by cephalosporins?

Answer 10

LAME: listeria, atypicals like chlamydia/mycoplasma, MRSA, enterococci. only exception is ceftarolin, which covers MRSA.

Question 11

1st gen cephalosporin: coverage/uses

Answer 11

covers PEcK: proteus, E coli, klebsiella.

used prior to surgery to prevent S. aureus wound infections

Question 12

2nd generation cephalosporins: coverage/uses

Answer 12

HEN PEcKS: Hib, Enetrobacter, Neisseria, Proteus, E coli, Klebsiella, serratia

Question 13

3rd generation cephalosporins

Answer 13

used for secrious gram negative infections resistant to other beta lactams. Ceftriazone is used for menigitis and gonorrhea, ceftazidime is used for pseudomonas.

Question 14

cefepime

Answer 14

4th generation cephalosporin. covers pseudomonas and other gram positive organisms

Question 15

ceftaroline

Answer 15

broad coverage, including MRSA. does NOT cover pseudomonas

Question 16

toxicity of cephalosporins

Answer 16

hypersensitivity, vitamin K deficiency. increases the toxicity of aminoglycosides

Question 17

Azotreonam: mechanism

Answer 17

monobactam resistant to beta lactamases. prevents peptidoglycan cross-linking by binding to pencillin binding protein 3. synergistic with aminoglycosides.

Question 18

azotreonam use and toxicity

Answer 18

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

Question 19

carbapenems: mechanism, special considerations

Answer 19

esp. imipenem. broad spectrum beta lactamase resistant carbapenem. always administered with cilastin to decrease inactivation of the drug in the renal tubules.

Question 20

Carbapenems: use and toxicities

Answer 20

gram positive cocci, gram negative rods, anaerobes. toxicities: can cause GI distress, skin rash, and CNS toxicity/seizures at high levels.

Question 21

Vancomycin mechanism and resistance.

Answer 21

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

Question 22

vancomycin use and toxicities

Answer 22

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.