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Pharmacology 1 > Antimicrobial Families > Flashcards

Antimicrobial Families Flashcards

1
Q

Physiochemical properties of beta-lactams

A
  • water soluble, organic acids (extracellular)
  • low to high protein binding
  • acid labile
  • metal ions can accelerate degradation process
  • chemically incompatible with aminoglycosides in vitro
  • initial fermentation product
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2
Q

Mechanism of action for beta lactams

A

Inhibit bacterial cell wall synthesis by binding to penicillin binding proteins
- cross linkage of peptidoglycan cell wall does not occur

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3
Q

Beta-lactams are typically ______ due to osmotic imbalance

A

Bacteriocidal

- bacteria cytoplasm is hypertonic compared to host isotonic environment

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4
Q

When does static action occur with beta lactams?

A

If bacteria treated with beta-lactams are in an environment isotonic to their cytoplasm

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5
Q

Which antibiotic class has decreased activity in the presence of purulent debris?

A

Beta lactams

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6
Q

MRSA implies resistance to _______

A

The entire beta lactam family

- resistance factors also carry resistance to a variety of other antibiotics

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7
Q

How does cefazolin differ from other first‐generation cephalosporins?

A

Is the only injectable 1st generation cephalosporin

  • has better activity against E coli
  • must be tested for gram neg susceptibility
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8
Q

Mechanisms of beta lactam resistance

A
  • degradation by bacterial enzymes
  • penicillin binding site alteration
  • reduced penetration (impaired crypticity)
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9
Q

What allows passage of resistance between species of bacteria and between genera?

A

Plasmids and transposons

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10
Q

What is the pharmacodynamics of penicillins?

A

Time-dependent killing

- you are not looking at how high peak concentration is

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11
Q

What beta-lactam is measured in units?

A

Penicillin G

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12
Q

All beta lactams concentrate in _______

A

Urine

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13
Q

What is the drug of choice for most streps and anaerobes?

A

Penicillin

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14
Q

What are the 3 forms of penicillin G and their concentrations?

A 
Crystalline (IV,IV,SQ)
- rapid high conc
- short duration
Procaine (IM,SQ)
- flip-flop kinetics
- lower conc, prolonged duration
Benzathene (IM)
- flip flop kinetics
- extremely low conc, prolonged duration (increased residue in food animals)
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15
Q

Penicillin G - adverse reactions

A

Nontoxic, primarily allergic rxns due to degradation product of penicilloic acid
- may have toxicity with salt (potassium pen G) or ester (procaine)

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16
Q

Why should pen G not be used in guinea pigs, hamsters, or rabbits?

A

Will disrupt hind gut flora

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17
Q

How is penicillinase-resistant penicillins similar to pen G?

A

Similar in structure, but is not inactivated by penicillinase
- use against staph that are resistant due to penicillinase

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18
Q

What 2 drugs are used to test bacteria against penicillinase-resistant penicillins?

A

Oxacillin or cefoxitin

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19
Q

Dicloxacillin

A 
Acid stable (can be given orally)
- approved for use in dogs, but 1st gen cephalosporins are used instead
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20
Q

Cloxacillin

A

Intramammary infusion for dairy cows

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21
Q

What are the 2 narrow spectrum penicillins?

A

Pen G and Penicillinase-resistant penicillin

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22
Q

What allows broad spec penicillins better penetration of gram negs?

A

Increased crypticity

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23
Q

What are the 3 broad spec penicillins

A
  • ampicillin
  • amoxicillin
  • hetacillin
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24
Q

Hetacillin

A

Prodrug converted to ampicillin by metabolism

- used as intramammary infusion

25
Q

Ampi and amoxicillin

A

Used interchangeably

  • acid stable (oral)
  • similar D, M, E as narrow specs
26
Q

Which broad spec is absorbed twice as well orally in dogs and cats as ampicillin?

A

Amoxicillin

27
Q

No _______ are absorbed orally in horses

A

Penicillins

28
Q

Injectable broad spec penicillins

A

Sodium ampi and sodium amoxi are given by all parenteral routes

  • rapid absorption and elimination (given every 8 hrs)
  • repository trihydrate formulation used in vet med
29
Q

How effective are the broad spec penicillins against enteric gram-neg?

A

Ampi/amoxicillin is unlikely to reach effective concentrations

  • S breakpoint in dogs/cats: 0.25 mcg/ml
  • S breakpoint in cattle: 0.03 mcg/ml
30
Q

Adverse reactions to broad spectrum penicillins

A
  • large doses of ampi can cause diarrhea in horses (entry into bile)
  • disrupts flora if given orally to ruminants
  • trihydrate form too irritating to use in horses
31
Q

When is it okay to give oral amoxi (extra-labelly) to a ruminant?

A

Only give to calves in their first 24 hrs while they are still considered to be a monogastric

32
Q

Extended spectrum penicillins

A

Anti-pseudomonal penicillins

  • increased crypticity, bind to altered PBP
  • ticarcillin, piperacillin
  • acid labile (6-8 hr dosing interval)
33
Q

Potentiated penicillins

A

Penicillinase inhibitor is added to formulation to “release” penicillin (ticarcillin, piperacillin)

  • clavulanic acid, sulbactam
  • inhibitor looses stability once hydrated, so need to have tablets well wrapped
  • only works in bacteria resistant by virtue of penicillinase
  • ineffective against bacterial strains containing type 1 beta-lactamases
34
Q

What potentiated penicillin is effective against chlamydia in cats?

A

Clavamox

35
Q

With cephalosporins, activity against anaerobes is ______

A

Erratic

- clostridia are highly resistant

36
Q

1st generation cephalosporins

A

Not affected by penicillinase, good activity against staph

  • used in skin and bone infections
  • not reliable against anaerobes
37
Q

1st gen cephalosporin agents

A
  • cephalothin - nepthrotoxic! still used for in vitro susceptibility test
  • cephalexin and cefadroxil - used as orals in small animals
  • cefazolin - better e coli activity than other 1st gens
  • cephapirin - intramammary infusion for dairy cows
38
Q

Which 1st gen ceph is injectable?

A

Cefazolin

39
Q

2nd generation cephalosporins

A
  • cefoxitin

- cefotetan

40
Q

Cefoxitin and cefotetan

A

Have good anaerobic acitivty!

  • 4 quadrant coverage!!
  • are structurally considered to be cephamycins (other cephalosporins are cephems) making them less suceptible to cephalosporinase produced by anaerobes
  • injectable only (IV, IM)
41
Q

What is an injectable, 4 quadrant drug of choice in a non-critical patient

A

Cefoxitin

42
Q

What 3rd gen cephalosporin is effective against pseudomonas?

A

Ceftazidime

43
Q

What causes resistance to 3rd gen cephalosporins to pseudomonas?

A

Extended spectrum beta-lactamases

- increasing public health concern

44
Q

Common 3rd gen injectables

A
  • cefotaxime
  • ceftriaxone (standard for meningitis)
  • ceftazidime
45
Q

What allows 3rd gens to cross the BBB?

A

Low MICs and low to moderate protein binding

- considered drug of choice for bacterial meningitis

46
Q

What cephalosporins are not effective against carbapenem-resistant enterobacteriaceae?

A

4th gen, 5th gen, and potentiated cephalosporins

- not used in vet med

47
Q

New-gen cephalosporins

A

Extensively protein bound causing long elimination half-lives and long dosing intervals
- goon non-enteric gram neg activity

48
Q

Ceftiofur

A

Rapidly metabolized to desfuroylceftiofur

- most activity comes from metabolite

49
Q

Cefpodoxime proxetil

A

Prodrug converted by intestinal wall esterases to active cefpodoxime

50
Q

Cefovecin

A

Structurally is a 3rd gen, but high protein binding

51
Q

Naxcel

A

Ceftiofur sodium

  • requires reconstitution with a limited shelf life
  • 4 day withdrawal for slaughter
  • no withdrawal for milk*
52
Q

Excenel

A

Ceftiofur HCL

  • shelf stable formulation
  • 2 day slaughter withdrawal no milk withdrawal
  • exception: spectramast intramammary infusion that does have a milk withdrawal
53
Q

Excede

A

Ceftiofur crystalline free acid

  • approved for cattle for 1 or 2 doses
  • -> 13 day slaughter withdrawal, no milk withdrawal
  • approved in swine (14 day slaughter withdrawal) and horses
54
Q

Cefpodoxime proxetil

A

Once daily oral dosing

- dogs used to treat skin and soft tissue infections

55
Q

Cefovecin

A

Labelled for skin and soft tissue infections due to staph, strep, and pasturella and for UTI due to e coli
- long duration due to high protein binding and long half life

56
Q

Monobactams

A

Spectrum limited to aerobic gram-neg bacilli

57
Q

Carbapenems

A

Broadest spectrum of activity of any antibiotics

  • penetrates BBB, inflammation enhances penetration
  • imipenem and meropenam
58
Q

Meropenem

A

Does not cause seizures or nephrotoxicity

- given SQ and IV

59
Q

Carbapenem-resistant enterobacteriaceae

A

Enterobacteriaceae resistant to all beta-lactams including carbapenems

  • reported in all 50 states
  • resistant mechanisms: carbapenemases, decreased crypticity, active efflux pump
  • horizontal transmission

Pharmacology 1 (15 decks)

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