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Pharmacology 3 > Beta-Lactams > Flashcards

Beta-Lactams Flashcards

1
Q

what is significant about Beta-lactams?

A

beta lactam ring critical for INactivation of drug

- beta lactamase enzyme

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2
Q

What are 4 penicillin Gs used in vet med?

A

Crystalline penicillin G (Na or K)

  • sterile human formulations or injection
  • vet forms in drinking water
  • IV/IM/SC

Procaine Penicillin G

  • white injectable
  • oral premixes
  • intramammar
  • IM or SC only

Benzathine Penicillin G

  • long acting injectable (duplocillin LA)
  • IM or SC only

Penicillin V (human)

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3
Q

What is the MOA of Penicillin G?

A

disrupting synthesis of bacterial cell wall

  • inhibits penicillin binding protein (PBPs) found on membrane
  • interferes with enzyme needed for peptidoglycan synthesis
  • lysis of cell in growing phase (bacteriocidal)
  • slow growing (bacteriostatic)
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4
Q

Why do penicillin Gs work better against gram +?

A

more peptidoglycans for enzyme interferance

high affinity for PBPs for B-lactams

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5
Q

What bacteria are susceptible to Penicillin Gs?

A

Many Gram + (not most staph)
most Anaerobes
Streptococcus
clostridium perfringens

other

  • gram + (actinomyces, truepurella pyogenes, some bacillus, corynebacterium, erisipelothrix rhusiopathiae, listeria)
  • gram - (histophilus, pasturella)
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6
Q

Which bacteria are resistant? why?

A

most gram -
- produces beta lactamase, cant penetrate cell wall, low affinity PBP)

Mst staph
- produce beta lactamase

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7
Q

How is Penicillin orally absorbed?

A

poorly (rapid hydrolysis in stomach acid)
exception: phenooxymethyl penicillin V)

Why in water?
- feed efficiency (impacts microflora)

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8
Q

How is Penicillin absorbed parenterally?

A

Crystalline Pen G: only dosage suitable for IV, rapid absorption IM or SC

Procaine Pen G: more slowly absorbed IM than crystalline, lower more sustainable concentrations, neck better than rump (carcass damage, absorption)
NEVER IV - death

Benzathine penicillin G: very slow absorption, sustained but oftn subtherpeutic doses

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9
Q

Which penicillin G should you never give IV?

A

Procaine Pen G

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10
Q

What is the distribution of Pen G?

A

weak acid = ionized in plasma = wont dsitribute well
low Vd
- good concentrations in plasma and ECF
- may not reach concentrations in some tissues
- increase distribution to tissues with inflammation

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11
Q

What is the elimination of Pen G?

A

very little metabolism

excretion: renal
- most via renal tubule by OATs
- short half life, longer with procaine and benzathine
- can only eliminate what is absorbed

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12
Q

What is the PK-PD relationship of Pen G?

A

time dependent

  • crystalline multiple a day
  • procaine - once a day
  • procaine/benz multiple days between
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13
Q

What is penicillin dosing measured in?

A

IU

1IU= 0.6ug

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14
Q

What are penicillin AE?

A 
hypersensitivity (type 1
autoimmune anemia (type 2)
vasculitis (type 3)
GI flora changes (diarrhea)
drug residues in food - inject in neck
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15
Q

What drug interactions should we be concerned about?

A

disrupt cell wall = increase aminoglycoside entry into cell

- little evidence

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16
Q

What are isoxazolyl penicillins?

A

used for anti-staphylococcal

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17
Q

How do they compare to Pen G?

A 
same bacteria (not as potent)
resistant to S. aureus penicillinase (used for staph)
18
Q

What is isoxazolyl penicillin used for?

A
  • mastitis (intramammary)

- methicillin resistant Staph aureus and pseudointermedius (MRSA,MRSP)

19
Q

how can isoxazolyl penicillins combat methicillin resistance?

A

mecAgene: code for PBP2A (low affinity for B-lactams)

- codes for different PBP

20
Q

What the spec of activity for isoxazolyl Pen?

A

staph aureus, strep agalactiae, clostridium perfringens
many gram + (staph
anaerobes

21
Q

What are two isoxazolyl penicillin drugs?

A

cloxacillin (intramammary suspension)

oxacillin

22
Q

Name two aminopenicillins and their use

A 
ampicillin 
trihydrate salt
- IM/SC in cattle, swine, dogs, cats
- NOT IV
- human injectable and oral

amoxicillin

  • oral tablets and suspensions
  • with or without clavulanic acid
  • many infections in dogs and cats
  • soluble powder for water (swine and poultry)
23
Q

What is aminopenicillin spec of activity?

A 
staph aureus - (add beta lactamase inhibitor for better effect)
strep agalactia
clostridium perfringens
many gram +
some gram -
anaerobes
24
Q

How does amino penicillin compare to Pen G?

A

same bacteria as Pen G (comparable potency)

amino allows for better penetration through outer layer of gram - bacteria than Pen G

still susceptible to B-latamase

25
Q

what is the aminopenicillin absoprtion?

A

oral
- ampicillin and amoxicillin are acid stable
injectable trihydrate (slow SC and IM)
ampicillin sodium (rapid IV)

26
Q

What is the aminopenicillin distribution, metabolism and elimination?

A

same as Pen g
short T1/2
BID for oral (time dependent)
SID for amipicillin trihydrate after IM

27
Q

What are the aminopenicillin drug interactions?

A

same as pen G

- synergy with aminopenicillins

28
Q

What are the aminopenicillin AE?

A

hypersensitivity
- less than Pen G
- cross reactivity
diarrhea

29
Q

What are three carboxypenicllins (anti-pseudomonal penicillins)?

A

carbenicillin
ticarcillin
pipercillin

all human formulations, IV with beta lactamase inhibittor

30
Q

What is the spectrum of activity of carboxypenicillins?

A 
gram - 
- except B-lactamse producers
- pseudomonas
anaerobes
decrease activity of Gram +
31
Q

What is the one beta-lactamase inhibitor?

A

clavulanic acid

  • oral tablets and suspensions for small animal
  • human formulations are diff
32
Q

What is the MOA of betalactamse inhibitors?

A

little antimicrobial on own

irreversibly bind to and activates b-lactamase enzymes allowing b-lactam to work on PBP

33
Q

What is the spectrum of activity of b-lactamase inhibitors?

A

gram +
- most B-lactamse producing staph (unless methicillin resistant)
Gram - some
anaerobes

34
Q

EXAM question: What if the PBPs are different? is the B-lactamase inhibitor still effective?

A

no they are ineffective

35
Q

What bacteria is resistant to ampicillin normally but susceptable if clavulanic acid is added?

A

staphylococcus intermedius

36
Q

What is B-lactamase inhibitor PK?

A

same as amoxicillin

37
Q

What are two carpapenems (extended spectrum penicillins)?

A

imipenem

  • rare usage
  • IV (IM or SC painful)
  • hydrolysed by dihydropeptidase enzymes in kidney = toxic metabolites (used with cilastatin, dihydropeptidase inhibitor)

Meropenem
- IV or SC

38
Q

What is the PK of both carbapenems?

A

short T1/2 with renal excretion

39
Q

What is the spectrum of activity for carbapenems?

A

wide spectrum
Gram +,-, anaerobes, resistant to B-lactamase enzymes
- last resort drug in human medicine

40
Q

Should carbapenems be used in vet med?

A

no

last resort in human

Pharmacology 3 (11 decks)

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