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Basic Pharmacology > Beta-Lactams > Flashcards

Beta-Lactams Flashcards

1
Q

what does ADME stand for?

A

absorption/route
distribution
metabolism
excretion

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2
Q

what are the mechanisms of action for beta-lactams?

A

inhibit cell wall synthesis
bactericidal

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3
Q

how do beta-lactams inhibit cell wall synthesis?

A

bind to penicillin binding proteins and reduce cross linking of the peptidoglycan cell wall

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4
Q

what is the most significant mechanism of acquired resistance?

A

production of beta-lactamases: acquired chromosomally or via plasmids/transposons

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5
Q

what are the mechanisms of resistance to beta lactams?

A

production of beta-lactamases
alteration of penicillin-binding protein
crypticity (drug property)
altered PBP

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6
Q

what is crypticity?

A

a drug property that contributes to resistance
ability to reach the site of action in gram negative bacteria

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7
Q

the mecA gene codes for a different PBP- PBP2a that ______________________________________________

A

does not allow binding by any beta-lactam

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8
Q

what type of mutation is the mecA gene that codes for a different PBP - PBP2a?

A

chromosomal

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9
Q

true/false: time above MIC is more important that how far above the MIC is reached for beta lactams

A

true

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10
Q

what is the most important adverse effect of beta lactams?

A

diarrhea/colic/disruption of fermentation
caution with use in hind gut fermenters

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11
Q

penicillin G is _____-labile

A

acid

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12
Q

who should you not use penicillin G in?

A

guinea pigs
caution in rabbits and chinchillas

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13
Q

what are the two main formulations of penicillin G?

A

crystalline
procain penicillin G: not IV

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14
Q

does penicillin G work on E coli?

A

no

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15
Q

does penicillin work on gram positives or gram negatives in general?

A

gram positives

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16
Q

what are some microbes that penicillin G works well for?

A

Streptococcus
anaerobes

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17
Q

what is a gram negative microbe that penicillin G works for?

A

Leptospirosis

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18
Q

what does increased crypticity of broad spectrum penicillins allow?

A

better penetration of gram-negative bacteria

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19
Q

can broad spectrum penicillins be given orally?

A

yes- acid stable
amoxicillin more bioavailable that ampicillin and is recommended for oral therapy (dogs and cats)

20
Q

what is Polyflex?

A

ampicillin trihydrate

21
Q

what is important about extended spectrum penicillins (with gram negatives)?

A

further increased crypticity and able to bind altered penicillin binding proteins
significant gram negative activity extending to Pseudomonas

22
Q

which pathogens can extended spectrum penicillins work against?

A

E. coli
Streptococcus
anaerobe
Leptospirosis
Pseudomonas

23
Q

what is done to potentiated penicillins?

A

penicillinase inhibitor is added to the formulation to “release” the penicillin: clavulanic acid, sulbactam

24
Q

potentiated penicillins only work in those bacteria resistant by virtue of __________________, not with altered penicillin binding protein

A

penicillinase

25
Q

how effective is amoxicillin-clavulanate against the four quadrants, and one more?

A

E. colo in urine, maybe not in tissue
Staphylococcus: ++
Streptococcus: +
anaerobe: +
Bacteroides fragilis: +

26
Q

do amoxicillin-clavulanate or piperacillin-tazobactam work against Rickettsia or Mycoplasma?

A

no

27
Q

what drug is effective against Leptospirosis and Pseudomonas?

A

piperacillin-tazobactam

28
Q

what is the structural feature of beta lactams that is a target for drug resistance?

A

beta lactam ring

29
Q

what is the distribution of beta lactams?

A

mostly extracellular
third generation cephalosporins and carbapenems are an exception to limited distribution and penetrate all tissue (including blood brain barrier)

30
Q

what is the metabolism of beta lactams?

A

limited

31
Q

how are beta lactams excreted?

A

renal filtration and excretion
concentrate in urine which can help their effectiveness with UTIs

32
Q

how are beta lactams bactericidal?

A

create osmotic imbalance between hypertonic bacterial interior and isotonic exterior: cell lysis

33
Q

how do beta lactams inhibit cell wall synthesis?

A

bind to penicillin binding proteins and reduce cross linking of the petidoglycan wall

34
Q

how does altered PBP contribute to resistance of beta lactams?

A

mecA gene codes for a different PBP: PBP2a
PBP2a does not allow binding of any beta lactam

35
Q

what type of mutation is the mecA gene?

A

chromosomal

36
Q

what does the mecA gene mutation imply resistance to?

A

almost all beta lactams including carbapenems

37
Q

why are there different targets for necessary time above MIC with beta lactams?

A

depending on drug and agent
due to post-antibiotic effect

38
Q

what is added to beta lactams to increase their effect (broad and extended spectrums)?

A

beta lactamase inhibitor

39
Q

can you give procain penicillin IV?

A

no

40
Q

what is the spectrum of Penicillin G with the 4 quadrants?

A

E coli: -
Staphylococcus: *
Streptococcus: +
anaerobe: +

41
Q

what are some broad spectrum penicillins?

A

aminopenicillins: ampicillin and amoxicillin

42
Q

is amoxicillin or ampicillin more bioavailable and recommended for oral therapy?

A

amoxicillin

43
Q

how can ampicillin trihydrate be given?

A

IM or SQ

44
Q

what is the efficacy of ampicillin and amoxicillin against the four quadrants?

A

E coli: +/-
Staphylococcus: *
Streptococcus: +
anaerobe: +

45
Q

what is one pathogen that ampicillin and amoxicillin are effective against that is not in the four quadrants?

A

Leptospirosis

46
Q

what is the efficacy of piperacillin (extended spectrum penicillins) against the four quadrants?

A

E coli: ++
Staphylococcus: *
Streptococcus: +
anaerobe: +

47
Q

what are the potentiateed penicillin formulations?

A

oral amoxicillin + clavulanic acid: clavamox or augmentin (human)
injectable ampicillin + sulbactam: unasyn (human)

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