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Y2 Pharmaco > Beta Lactams & Vancomycin > Flashcards

Beta Lactams & Vancomycin Flashcards

1
Q

What is the structural difference of gram +ve and gram -ve bacteria?

A

Gram +ve: (stained blue-black)
1. Thick peptidoglycan & lipoteichoic layer
2. Lacks outer membrane

Gram -ve: (stained pink red)
1. Thin peptidoglycan layer
2. LPS in outer membrane (lipopolysaccharide)

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2
Q

Name the 2 broad types of cell wall synthesis inhibitors.

A
  1. Beta-lactams
  2. Glycopeptides - aka vancomycins
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3
Q

Name the 4 categories of beta lactams.

A
  1. Penicillin
  2. Cephalosporin/Cephamycins
  3. Carbapenems
  4. Monobactam
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4
Q

When should antibiotics be administered?

A

In presence of:
- acute, severe, rapidly spreading infection

No need in case of:
- mild, localised infection in which drainage can be established

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5
Q

What are β-lactam antibiotics?

A

β-lactam antibiotics consist of the 4-membered β-lactam ring
- fused to either 5 / 6 membered ring via single/double bond
- if fused to nothing => monobactam

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6
Q

MOA of beta-lactams.

A

TLDR: inhibits cross-linking, aka interferes w transpeptidation

  1. In cell, transpeptidase catalyses the cross-linking of terminal peptidoglycan proteins in linear polymer chains for cell wall synthesis
  2. β-lactam ring binds to active site of transpeptidase => prevents cross-linking
  3. Cell wall weakened => lysis when intracellular pressure increases above surrounding osmotic pressure (in actively growing cell)

Key! If bacteria is static & not actively growing, then the beta lactam doesnt rly have much to interfere w, not as effective

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7
Q

Name the 4 classes of Penicillins.

A
  1. Natural Penicillins
  2. Penicillinase resistant penicillins
  3. Aminopenicillins (Broad Spectrum) + BL inhibitors
  4. Anti Pseudomonal penicillins (extended spectrum) + BL inhibitors

NPAA

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8
Q

Name the 2 types of Natural Penicillins & their differences.

A
  1. Penicillin G
    - low oral bioavailability
    - administered parentally (IV or IM)
  2. Penicillin V
    - better oral bioavailability than G, cuz more acid stable
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9
Q

Limitation of Natural Penicillin.

A
  1. Only useful against bacteria that do not produce β-lactamase!! => thus, useless against most staphs
    - β-lactamase/penicillinase will cleave the β-lactam ring and render the antibiotic useless
  2. Not useful against amoebae, plasmodia, fungi or viruses
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10
Q

What is Natural Penicillin useful against?

A

Useful against β-lactamase negative strains such as:
1. Gram +ve microbes
E.g. streptococci, bacillus diphtheriae
2. Some Gram -ve microbes
E.g. meningococci, gonococci
3. Obligate anaerobes eg. Clostridum spp

Only on non β-lactamase producing bacteria

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11
Q

How is Natural Penicillin excreted?

A

Renal clearance, excreted in urine

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12
Q

Why is there a need for Penicillinase-resistant penicillins?

A

They cover penicillinase producing staphylococci, which natural penicillins are helpless against.
(Rmb the beta-lactamases that staphs produce)

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13
Q

How is Penicillinase-resistant penicillin cleared & excreted

A

Renal clearance, excreted through urine

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14
Q

What is the short coming of penicinillase-resistant penicillin?

A

Narrow cover antibiotics
- only covers gram +ve bacteria
- no coverage against gram -ves

+

Does not achieve therapeutic levels as it has limited penetration into CSF

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15
Q

What was the 1st gen penicillinase-resistant penicillin and its significance?

A

Methicillin.

Where MRSA gets its name from. Methicillin-resistant staphylococcus aureus.
- MRSA are staphylococci strain that modified its transpeptidase enzymes such that they have a low affinity to the β-lactam ring
- so transpeptidase in MRSA is not easily inhibited

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16
Q

Why are Penicillinase-resistant penicillins more resistant to penicillinase?

A

Presence of bulky side chain!
- protects the beta-lactam ring from beta-lactamase
- by limiting their accessibility to the catalytic site of action

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17
Q

Name the commonly used penicillinase-resistant penicillins used today.

A
  1. Cloxacillin
  2. Oxacillin
  3. Flucloxacillin
  4. Methicillin (1st gen that is not longer used)
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18
Q

Why are Aminopenicillins and what is their importance?

A
  1. Broad Spectrum penicillins
    - covers both gram +ve & gram -ve
    - (non β-lactamase prducing)
  2. Acid stable => available both orally & via IV
  3. Commonly used in many diff types of dental infections (cuz of oral admin + broad spec)
    - prophylaxis against infective endocarditis
    - against aggressive periodotitis
    - dental abscesses
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19
Q

Name 2 aminopenicillins.

A
  1. Ampicillin (acid stable, available orally & IV)
  2. Amoxicillin (better oral absorption than ampicillin, IV)
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20
Q

Limitations of aminopenicillins.

A

Does not cover:
1. Bacteria that produce beta-lactamase
2. Pseudomonas or Klebsiella

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21
Q

How are aminopenicillins cleared & excreted?

A

Renal clearance, excreted via urine
- dose adjustment needed in pxs w renal dysfunction

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22
Q

Why are aminopenicillins not only effective against gram +ve bacteria, but also against gram -ve bacteria? (MOA)

A
  • additional hydrophilic group allows penetration into gram -ve bacteria via porins
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23
Q

What is commonly administered w aminopenicillins?

A

β-lactamase inhibitors!

  • addition of β-lactamase inhibitor can extend the spectrum of use to β-lactamase producing strains

E.g. Augmentin = Amoxicillin (aminopenicillin) + Clavulanic acid (β-lactamase inhibitor)

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24
Q

Name the most notorious hospital acquired infections.

A

Klebsiella & Pseudomonas
- gram -ve bacterias

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25
Q

Name a Anti Pseudomonal Penicillin. How is it administered?

A

Piperacillin. Administered only via IV

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26
Q

How are Anti-Pseudomonal Penicillins cleared and excreted?

A

Primarily renal clearance, excreted via urine.
- dose adjustment needed in px w renal dysfunction

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27
Q

Piperacillin is commonly given w _________. Why?

A

Tazobactam. (β-lactamase inhibitor)

  • cuz piperacillin is susceptible to inactivation by bacterial β-lactamase pdn
28
Q

What is the significance of Anti-Pseudomonas Pencillins?

A

TLDR: widest coverage (covers pseudomonas & klebsiella & both grams) + wide anaerobic coverage

  • has greatest activity against Pseudomonas & Klebsiella: gram -ve bacteria
29
Q

What are β-lactamase inhibitors?

A

TLDR: binds irreversibly to β-lactamases, protecting other β-lactam antibiotics from being targeted by β-lactamases

Also: has very weak anti-bacterial properties

30
Q

Name the 3 common β-lactamase inhibitors

A
  1. Clavulanic acid
  2. Tazobactam
  3. Sulbactam
31
Q

Name the 3 common β-lactamase combination drugs.

A
  1. Augmentin = amoxicillin + clavulanic acid
  2. Unasyn = ampicillin + sulbactam
  3. Zosyn = Piperacillin + Tazobactam

All can administered via IV, additionally, augmentin can be orally administered.

32
Q

Which penicillin classes are commonly administered w beta-lactamase inhibitors?

A

Ans: aminopenicillins & anti-pseudomonal penicillins

Not natural penicillins & not penicillinas resistant penicillins (these alr r efficient against beta-lactamase pdc bacteria)

33
Q

What are the mechanisms of resistance to penicillin?

A
  1. Transpeptidase altered, reduced affiinity for the penicillins
  2. Pdn of β-lactamase, hydrolyses β-lactam ring
  3. Bacteria decreases porin pdn => decrease in intracellular drug conc
  4. Presence of efflux pumps
34
Q

What are the 6 common adverse reactions to penicillin?

A
  1. Allergy/Hypersensitivity
    - Stevens Johnson syndrome (SJS), toxic epidermal necrolysis (TEN)
  2. CDAD: clostridium difficile-associated diarrhoea
    - due to ampicillin/augmentin
  3. Neurotoxicity
    - due to high dose & renal dysfunction
  4. Hepatotoxicity
  5. Anosmia
  6. Seizures, in px w renal failure
35
Q

List the 6 possible common adverse effects of penicillin.

A
  1. Allergy/hypersensitivity
    - stevens johnson syndrome(SJS) & toxic epidermal necrolysis(TEN)
  2. CDAD: clostridium difficile-associated diarrhoea
  3. Neurotoxicity
  4. Hepatoxicity
  5. Anosmia
  6. Seizures, in px w renal impairment
36
Q

What are some drug drug interactions of penicillin?

A
  1. Penicillins/cephalosporins + anti-coagulants (e.g. warfarin) => increased risk of bleeding
  2. Probenecid inhibit tubular secretion of penicillin (esp amoxicillin) => delays excretion
37
Q

Which 1st gen Cephalosporin is administered via IV?

A

Cefazolin
- rest are administered orally

38
Q

How are Cephalosporins administered?

A

1-2 gen: mostly orally (except cefazolin)
3 gen onwards: IV/IM

39
Q

3rd gen cephalosprins and below are..

A
  1. more resistant to beta lactamases
  2. have better CSF distribution
  3. better activity against anaerobes
40
Q

What is special about Cefotaxime?

A

3rd gen cephalosporin that covers pseudomonas, enterobacteriaceae, neisseria gonorrhea

41
Q

What is special about Cefepime?

A

4th gen Cephalosporin, covers pseudomonas

42
Q

What is special about Ceftaroline

A

5th gen Cephalosporin. covers MRSA

43
Q

Name the Cephalosporins that are 3rd gen and above.

A

3rd gens: cefotaxime, ceftazidime, ceftriaxone
4th gen: cefepime
5th gen: ceftaroline

44
Q

What is Ceftriaxone?

A
  • 3rd gen cephalosporin
  • used in pxs w renal impairment, since its the only cephalosporin that is excreted hepatically
45
Q

Adverse effects of Cephalosporins?

A
  1. Cross-hypersensitivity w penicillins
  2. Thrombophlebitis (increased risk of blood clot formation) /increased bleeding
  3. GIT: CDAD
46
Q

Carbapenems are the first line agent against..

A
  • ESBLs. Extended spectrum beta-lactamase producing gram neg bacteria
  • good coverage against anaerobic bacteria too
47
Q

How are Carbapenems administrated?

A

IV.

48
Q

Name the 3 Carbapenem drugs

A
  1. Imipenem & Cilastatin (Tienam)
  2. Meropenem
  3. Ertapenem
49
Q

What is Cilastatin?

A

DHP1 inhibitor => so that more Imipenem avail
- cuz Imipenem is rapidly hydrolyzed by DHP1 found in the brush border of proximal renal tubule

*not a beta-lactamase inhibitor!!

50
Q

Name the Carbapenems that are stable against hydrolysis by DHP1

A

Meropenem & Ertapenem.

  • Imipenem is quickly hydrolysed in proximal renal tubule, thus, administered w Cilastatin to recover more of the active form
51
Q

How are Carbapenems cleared and excreted?

A

Renal clearance, excreted in urine

52
Q

Do Carbapenems cover Pseudomonas?

A

Imipenem and Meropenem have coverage against Psuedomonas.

Ertapenem NO COVERAGE against pseudomonas aeroginosa & enterococcus spp

53
Q

Briefly list the adverse effects of carbapenems.

A
  1. GIT-related symptoms
    - nausea, vomiting (occurs more w Tienam)
  2. Rashes
  3. Neurotoxicity
  4. Cross-hypersensitivity w penicillin
54
Q

Monobactam acts against..

A
  1. Gram neg bacteria & 2. β-lactamase producing gram neg bacteria
    * no activity against +ves & anaerobes

E.g.
- enterobacteriaceae
- Pseudomonas
- klebsiella
- E. Coli

55
Q

Name the only Monobactam.

A

Aztreonam

56
Q

Monobactams have no activity against..

A

Gram positive bacteria & anaerobes

57
Q

Administration of Aztreonam.

A

IM/IV
- penetrates BBB in inflamed meninges

58
Q

Adverse effects of Aztreonam

A
  • generally well tolerated
  • occasional skin rashes
  • little or no cross-sensitivity w penicillins
59
Q

Aztreonam is cleared and excreted via

A

Renal clearance, excreted in urine

  • dose reduction req in renal impairment pxs
60
Q

What does Vancomycin target to prevent cell wall synthesis (MOA)

A
  • targets transglycosylases
  • unlike beta lactams that target transpeptidases
61
Q

What are Vancomycins used against (coverage)

A

Effective only against gram +ves.

  1. staph aureus (both MSSA & MRSA)
  2. Streptococci (both penicillin resistant & sensitive strains)
  3. Clostridium spp (administered orally)
  4. Enterococcus
  5. Bacillus spp
62
Q

Administration of Vancomycin.

A

IV for systemic treatment
Oral for CDAD or more severe AAPMC (antibiotic-associated pseudo-membranous colitis)

63
Q

Vancomycin is cleared and excreted via..

A

Renal clearance, excreted via urine

  • dose adjustment in px w renal impairment
64
Q

What bacterial species are resistant to Vancomycin?

A

Gram neg bacilli & mycobacteria

65
Q

Briefly list the adverse reactions of taking Vancomycin.

A
  1. Red man syndrome
    - occurs when Vancomycin is administered too quickly
    - due to histamine release in the face & upper torso
  2. Nephro & Oto toxicity
    - esp if px has renal impairment
    - similar to aminoglycosides
  3. Thrombophlebitis w fever & chills
  4. Cat C for pregnancy in parenteral formulations
66
Q

Name 2 instances of Vancomycin resistance

A
  1. Enterococcal resistance (VRE)
  2. S. Aureus => reduced/intermediate susceptibility (VRSA)
    - major concern as it is until recently where vancomycin was the only AB that staph was reliably susceptible

Y2 Pharmaco (22 decks)

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