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ID Review > Antibacterial Drugs > Flashcards

Antibacterial Drugs Flashcards

1
Q

What are the targets for selective toxicity?

A
  • Cell wall synthesis (Inhibitors of cell wall synthesis)
  • Membrane integrity
  • Protein synthesis (IPS)
  • Nucleic acid synthesis
  • Nucleic acid integrity
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2
Q

Beta-lactam antibiotics and vancomycin block

A

Enzymatic steps outside of the cell or in the periplasmic space
Other ICWS inhibitors act at IC sites

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3
Q

Penicillins

A

Very selective toxicity (extremely high chemotherapeutic index)
Bactericidal in growing, proliferating cells
Primarily used for gram (+)

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4
Q

Penicillin MOA

A
  1. Covalent binding to transpeptidases/penicillin binding proteins
  2. Inhibition of transpeptidation reaction (Cross-linking of cell wall)
  3. Activation of murein hydrolases (autolysins)
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5
Q

Penicillin Pharmacokinetics: Absorption

A
  • Many penicillins are acid-sensitive but can be still given orally
  • Parenteral penicillins: IV, IM (depo)
  • Benzathine penicillin: IM, insoluble, time release, compliance issues
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6
Q

Penicillin Distribution

A
  • Penicillins do not get across the blood-brain barrier, eye, ocular fluid, prostate
  • Meningitis may facilitate crossing blood-brain barrier
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7
Q

Penicillin Excretion

A
  • Penicillins excreted by tubular secretion (actively secreted by Organic Acid Secretory System, blocking this with Probenecid extends half-life)
  • Exceptions: Nafcillin secreted in bile, Oxa- and Cloxa- in urine and bile
  • Penicillins are rapidly cleared (1/2 life 30-60 min)
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8
Q

Time above minimal bacterial concentration (MBC)

A

relates to efficacy

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9
Q

Cell wall synthesis inhibitors (Penicillin, Cephalosporins, and Vancomycin) exhibit

A

Time-Dependent Killing (concentration independent). Need extended half life to work effectively.

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10
Q

Pen G and Pen V are primarily useful against

A

Gram (+)

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11
Q

Staph became rapidly resistant to anti-staphylococcal penicillins b/c

A

The target of anti-staphylococcal penicillins is beta lactamase (which rapidly mutated)

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12
Q

Anti-staphylococcal penicillins

A

Nafcillin, Methicillin, Isoxazoyl penicillins (ox-, clox-)

Beta-lactamase resistant

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13
Q

Extended Spectrum penicillins

A

Ampicillin, Amoxicillin, Ticarcillin, Piperacillin, Mezlocillin
Developed to increase gram (-) activity (broader spectrum)
Can get through lipid membrane

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14
Q

Anti-pseudomonal penicillins

A

Exclusively for pseudomonal infections!

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15
Q

Adverse effects of penicillins

A

Ampicillin rash

Hypersensitivity reaction

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16
Q

Resistance to Penicillins

A
  1. No cell wall, no activation of murein hydrolases, metabolically inactive
  2. Inaccessible PBPs
    - gram (-)
    - Methicillin-resistant Staph. aureus (MRSA)
  3. Beta-lactamase production
    - Major mechanism of resistance
    - Plasma mediated
    - Use beta-lactamase resistant penicillin (Nafcillin, Oxacillin, Cloxacillin)
    - Co-administer Beta-lactamase inhibitor (Clauvanic acid, Sulbactam, Tazobactam)
17
Q

Problems associated with Penicillin use/overuse

A

Sensitization
Selection for resistant strains (90% of staph are resistant)
Superinfections by resistant organisms (esp. proteus, pseudomonas, serratia, fungi)

18
Q

Cephalosporins

A 
Structure and function similar to penicillins
Less sensitive to beta-lactamases
Broader spectrum of activity
Poor oral absorption
Renal toxicity
Cross-reactivity with penicillin
More expensive than penicillin
Secondary to ICWS: If a penicillin would work, use it
19
Q

1st generation cephalosporins

A

only effective against (+) bacteria

20
Q

Subsequent generation cephalosporins

A

Greater gram (-) activity
Some with less gram (+) activity (2nd generation)
Less beta-lactamase sensitivity
Cephalosporin resistant (especially 4th generation, Cefepime)
Decreased toxicity
Better distribution to CNS

21
Q

1st Generation Cephalosporins

A

Narrow spectrum
Cefazolin
Cephalexin (o)

22
Q

2nd Generation Cephalosporins

A

Intermediate spectrum
Cefuroxime (o)
Cefotetan
Ceflacor (o)

23
Q

3rd Generation Cephalosporins

A

Broad spectrum

Cefotaxime, Ceftriaxone, Ceftazidime, Cefpoxodime (o)

24
Q

4th Generation Cephalosporins

A

Broad spectrum

Cefepime

25
Q

Cephalosporine adverse effects

A

Local irritation from injection
Renal toxicity (enhanced by aminoglycosides)
Cefotetan and Cefoperazone can cause Disulfram Effect (Bleeding and platelet disorders, administer vitamin K)
Hypersensitivity: cross-reactivity with penicillin

26
Q

Monobactum: Aztreonam

A

Gram (-) activity; inactive against Gram (+) or anaerobes
Beta-lactamase resistant
Crosses blood-brain barrier
No cross-reactivity with penicillin

27
Q

Carbanepems: :Imipenem

A

Broad spectrum: Gram (+) and Gram (-) anaerobes
Beta-Lactamase resistant
Pseudomonas develops resistance rapidly, use with aminoglycosides
IV only
Cross blood-brain barrier
Inactivated by renal dipeptidase so co-administer Cilastatin
Low cross-reactivity with penicillin

28
Q

Meropenem

A

Dipeptidase-resistant carbapenem

29
Q

Vancomycin

A

Inhibits transglycosylation (step before transpeptidation)
Bactericidal for gram +IV for systemic use, oral for C difficile
Systemic: MRSA (synergistic with aminoglycosides)
IV drug cleared through kidney: enhances oto and renal toxicity of aminoglycosides
Red man or neck syndrome: histamine release
Misuse/overuse is problem
Vacomycin-dependent Enterococci

30
Q

Fosfomycin

A

Newest ICWS; Gram (+) and (-)

  • Inhibits cytoplasmic step in cell wall precursor synthesis
  • Active uptake by G6P-transporter
  • Oral and parenteral
  • Active drug excreted by kidney
  • Single dose approved for UTI
  • Synergistic with Beta-lactams, aminoglycosides, or fluoroquinolones
31
Q

Bacitracin

A 
Markedly nephrotoxic
Topical antibiotic (OTC only)
32
Q

Membrane-active drugs: Polymixins

A

Polymixin B and Polymixin E (Colistin)
Basic peptides (detergents)
Active against gram (-) except Proteus and Neisseria
Topical use due to systemic toxicity (renal)
Salvage therapy for highly resistant strains of Acinetobacter, Pseudomonas, and Enterobacteriae

ID Review (23 decks)

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