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Multisystems: Pharmacology > Cell-Wall Antibiotics > Flashcards

Cell-Wall Antibiotics Flashcards

1
Q

All cell-wall synthesis inhibitors are?

A

Bactericidal

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2
Q

Where is the weakest bond in a Beta-LACTAM?

A

Between the Nitrogen and Carbonyl Group (site of Beta-Lactamases)

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3
Q

Mechanism of action of ALL LACTAMS

A
  1. Bind PBPs 2. Inhibit transpeptidation 3. Inhibit cross-linking (final step in cell-wall synthesis)
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4
Q

Mechanism of resistance to ALL LACTAMS

A
  1. Beta-Lactamases
  2. Structural change in PBPs
  3. Change in porin structure (only Gram -)
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5
Q

How is MRSA resistant?

A

Structural change in PBPs (D.O.C. = Vancomycin)

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6
Q

How is Pseudomonas resistant?

A

Change in porin structure

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7
Q

Narrow Spectrum, Beta-Lactamase Sensitive

A

Penicillin G (IV) and Penicillin V (oral)

Good for Treponema pallidum (spirochete)

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8
Q

Very Narrow Spectrum, Beta-Lactamase Resistant

A

Nafcillin, Methicillin, Oxacillin

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9
Q

Treat what with Nafcillin, Methicillin, or Oxacillin?

A

Sort of a trick question…MSSA is NEVER treated with Methicillin (use Nafcillin instead)

Methicillin is only good, in the lab, for determining if a strain is sensitive (MSSA) or resistant (MRSA)

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10
Q

Broad spectrum, Aminopenicillins, Beta-Lactamase Sensitive

A

Ampicillin (IV) and Amoxicillin (Oral)

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11
Q

Extended spectrum, Antipseudomonal, Beta-Lectamase Sensitive

A

Ticarcillin, Piperacillin, Azlocillin, Carbenicillin

(increased activity againt gram - rods, including Pseudomonas)

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12
Q

Clavulanic acid, Sulbactam, and Tazobactam

A

“Suicide Inhibitors”

Used in combination with Penicillins. Beta-Lactamase metabolizes them to a product that inhibits itself (i.e., Beta-Lactamase Inhibitors)

Clavulanic = Oral

Sulbactam = IV

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13
Q

How are Nafcillin and Oxacillin eliminated?

A

In bile (all other drugs are eliminated via tubular secretion)

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14
Q

Side effects of Penicillins

A
  1. Hypersensitivity
  2. GI distress (killing exogenous flora in the gut)

*Jarisch-Herxheimer reaction in treatment of syphilis

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15
Q

Mechanism of action/resistance of Cephalosporins

A

Identical to penicillins

(Bind PBPs, Inhibit Transpeptidation, Inhibit Cross-Linking)

[Beta-Lactamases, Change in PBPs, Change in Porin Structure]

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16
Q

Organisms not covered by cephalosporins

A

“LAME”

Listeria, Atypicals (e.g., chlamydia, mycoplasma, urea),

MRSA, and Enterococci

Treat L with amoxicillin, A with macrolides, M with vancomycin, and E with amoxicillin

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17
Q

Ampicillin and Amoxicillin are used to treat what?

A

H.E.E.L.P.S.S

H. Influenza, E. Coli, Enterobacter, Listeria, Proteus, Salmonella, Shigella

Borrelia burgdorferi (Lyme disease)

NOTE: giving ampicillin/amoxicillin to someone with mono will result in a generalized rash (patient is not allergic, it is a consequence of the EBV interaction)

18
Q

First generation cephalosporins

A

Cefazolin and Cephalexin (+ anything with “ph”)

19
Q

What is Cefazolin used for?

A

PEcK

Proteus, E. Coli, Klebsiella

COMMON USE in SURGICAL PROPHYLAXIS (long duration of action)

20
Q

What is Ticarcillin used for?

A

Increased activity against gram (-) rods, including Pseudomonas

Usually combined with Tazobactam

21
Q

Second generation cephalosporins

A

Cefoxitin, Cefotetan, Cefaclor, and Cefuroxime

HENS PEcK

H. Influenza, Enterobacter, Neisseria, Serratia, Proteus, E. Coli, Klebsiella

Pneumonic = Fur, Fox, Tea

22
Q

Third Generation Cephalosporins

A

Ceftriaxone (IM), Cefotaxime (parenteral), Cefidinir and Cefixime (oral),Ceftazidime

23
Q

Use of Ceftriaxone & Ceftazidime

A

Third generation cephalosporins:

Empiric management of MENINGITIS and SEPSIS

Note: Both Ceftazidime and Cefepime (4th generation) are useful against pseudomonas

*Ceftriaxone is used commonly in “real life” and will often NOT be the correct answer on tests (look for the drug that doesn’t cover everything, just specifically what the question asks for)

24
Q

Cefepime

A

Fourth Generation Cephalosporin:

Even wider spectrum, resistant to most beta-lactamases, enters CNS

IV

25
Q

Probenecid

A

Blocks active tubular secretion of penicillins and cephalosporins (i.e., prolongs their effects)

26
Q

Side effects of cephalosporins

A
  1. Hypersensitivity: assume complete cross-allergenicity b/w individual cephalosporins and partial cross-allergenicity with penicillins (5%)
  2. Positive Coombs test, but hemolysis is rare
  3. Disulfiram-like effects (i.e., hangover)

*Most authorities recommend avoiding cephalosporins in patients allergic to penicillins

27
Q

Allergic to penicillin and infected with gram (+) organism

A

Consider macrolides

28
Q

Allergic to penicillin, infected with gram (-) organism

A

Consider aztreonam

29
Q

Mechanism of action for Imipenem, Meropenem, and Ertapenem (broad class = Carbapenems)

A

Same as penicillins and cephalosporins BUT resistant to Beta-Lactamases

*Imipenem is given w/ cilastatin (renal dehydropeptidase inhibitor) which inhibits metabolism to a nephrotoxic metabolite

*All drugs under renal elimination (decrease dose in renal dysfunction)

30
Q

What are Carbapenems commonly used for?

A

Empiric use in severe life-threatening nosocomial infections

Gram (+) cocci, Gram (-) rods [including pseudomonas], and anaerobes

NOT USEFUL AGAINST MRSA

31
Q

Side effects of “-penem’s”

A
  1. GI stress
  2. Drug fever (partial cross-allergencity with penicillins)
  3. CNS effects, including seizures in OD or renal dysfunction
32
Q

Aztreonam

A

Same MOA as penicillins and cephalosporins (binds PBP3)

Resistant to Beta-Lactamases

Monobactam

IV drug active against gram (-) rods

NO CROSS-ALLERGENICITY W/ PENICILLINS OR CEPHALOSPORINS

33
Q

MOA for Vancomycin

A

NOT A LACTAM…

  1. Binds at D-ala-D-ala muramyl pentapeptide
  2. Sterically hinders transglycosylation rxns involved in elongation
  3. Indirectly prevents transpeptidation

*DOES NOT interfere with PBPs

34
Q

Spectrum for Vancomycin

A

MRSA

Enterococci

Orally for C. Difficile (after metronidazole)

35
Q

Resistance to Vancomycin

A
  1. VRSA and VRE
  2. Change in muramyl pentapeptide target:

D-ala-D-ala replaced w/

D-ala-D-lac

36
Q

Pharmacokinetics of Vancomycin

A
  1. Used IV (orally for colitis b/c it is not absorbed)
  2. Enters most tissues (e.g., bone), but not CNS
  3. Eliminated by renal filtration
37
Q

Side effects of Vancomycin

A

N.O.T. Red

  1. “Red man syndrome” (histamine release)
  2. Ototoxicity (permanent)
  3. Nephrotoxicity (mild, but additive with other drugs)
  4. Thrombophlebitis
38
Q

If a patient suffers from “red man syndrome,” what are the nexts steps you need to take?

A
  1. Give anti-histamines and discontinue vancomycin
  2. After symptoms cease, deliver vancomycin at a lower dose
    * This is not considered an allergy and treatment can continue*
39
Q

Cell Wall Inhibitors that are effective against Pseudomonas

A

Cefepime and Ceftazidimine

Aztreonam

Carbapenems

Ticarcillin, Piperacillin, Carbenicillin

40
Q

In general, what happens when you move from 1st generation cephalosporins to 4th generation?

A

Sacrifice gram (+) coverage for increased gram (-) coverage

Multisystems: Pharmacology (11 decks)

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