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DWT Exam 2 > Pharmacology 4: Antibacterial agents for systemic therapy > Flashcards

Pharmacology 4: Antibacterial agents for systemic therapy Flashcards

1
Q

What do beta-lactam antibiotics include?

A

Penicillins

Cephalosporins

Carabapenems
-imipenem and meropenum

Monobactams
-aztreonam

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2
Q

What is beta-latam antibiotics mechanism of action?

A

Penerate the OUTER cell wall

Bind to and INHIBIT penicillin binding proteins (PBPs)
- Transpeptidase enzymes required for cross-linking of cell wall precursors

INHIBITION of cross-linking
- opens channels through the cell wall to create pores
- Allows fluid into the cell, causing cell swelling and DEATH

BACTERICIDAL

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3
Q

What are the general pharmacokinetics in beta-lactam antibiotics?

A

Low plasma protein binding
- distribute well to the EXTRAcellular fluid in most tissues
- EXCEPTIONS: cefovecin, ceftiofur

Hydrophilic
- minimalINTRAcellular concentrations
- do NOT distribute well to protected sites (CNS, eye, prostate)

Metabolism
- minimal
- EXPCEPTIONS: ceftiofur

Elimination
- glomerular filtration & tubular secretion
- VERY HIGH CONCENTRATIONS IN URINE!!! 1000X HIGHER THAN PLASMA!!!!

Short half-life and require frequent dosin
- EXCEPTIONS: cefovecin, ceftiofur crystalline free acid

Some PAE against gram + bacteria
- penicillin and streptococci

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4
Q

What are the pharmodynamics of beta-lactam antibiotics?

A

Time-dependent
-T>MIC 50% of the dosing interval
- minimum
- some people say 80%
– gram -

If immunosupprssed
-T> MIC 90-99%
-constant rate infusions

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5
Q

Benzylpenicillins 4 different kinds are?

A

Penicillin G

First beta-lactam

First penicillin

First antibiotic

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6
Q

What is Benzylpenicillin still effective against?

A

Streptococcus species

anaerobes (clostridia)

Gram - bacteria usually:
-e.coli, klebsiella, pseudomonas

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7
Q

What is Benzylpenicillin inactivated by beta-lactamases like?

A

Staphylococci +/-

Bacteroides fragilis (anaerobe)

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8
Q

What is the spectrum of Benzylpenicillins?

A

Gram +

streptococci ANAEROBES

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9
Q

Penicillin G routes and forms of drug?

A

Oral absorption limited
- degraded in gastric acid

IV formulations
-potassium or sodium salt
-human products expensive

IM/SQ formulations
-complexed with procaine or benzathine
-longer half-lives and be dosed less frequently
-veterinary products INEXPENSIVE

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10
Q

Penicillin G effect of formulation is on what?

we do NOT like this

A

PK

Efficacy

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11
Q

What species do we use Aminopenicillins FREQUENTLY?

A

CATS

dogs

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12
Q

Describe Aminopenicillins?

A

Drugs in class
- ampicillin
-amoxicillin

Good oral absorption in small animals
-BETTER amoxicillin
-ampicillin more IV/IM/SQ

Limited to NO oral absorption in large animals

INCREASED SPECTRUM AGAINST GRAM- BACTERIA
-LOWER UNIARY TRACT
-still maintain activity against gram+ and anaerobes

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13
Q

Extended spectrum penicillins

AKA carboxypenicillins

A

Drugs:
Ticarcillin
PIPERACILLIN
Carbenicillin

Reserved for highly resistant gram- bacteria and anaerobes
- Pseudomonas

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14
Q

Describe Anti-staphylococcal penicillins?

A

Drugs:
Methicillin
oxacillin

Little activity against gram- or anaerobic organisms

Methicillin (oxacillin) resistant staph. (MRSA/MRSP)
-bacteria reported resistant to oxacillin should be considered to be resistant to all other beta-lactam antibiotics

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15
Q

Are Anti-staphylococcal penicillins used clinically?

A

NO

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16
Q

What are the classifications for Cephalosporins?

A

1st generation
2nd generation
3rd generation
4th generation

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17
Q

Describe 1st generation cephalosporins?

A

Active against gram + bacteria, including some beta-lactamase + staphylococci

Includes:
- cefazolin
- has MOST activity against gram- bacteria
-cefadroxil
-cephalexin
- VERY commonly described to DOGS

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18
Q

Describe 2nd generation cephalosporins?

A

Greater activity against gram- bacteria
-in general

Activity against gram+ bacteria is similar

Includes
-cefoxitin
-cefotetan
-cefaclor

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19
Q

Describe 3rd generation cephalosporins?

A

MOST activity against gram- bacteria

Still retain activity against gram+
-lesser
-NOT used clinically - injudicious

Includes:
-ceftiofur
-cefovecin
-cefpodoxime proxetil
- human drugs
–> Ceftazidime and cefotaxime- Pseudomonas, CNS infections

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20
Q

Describe 4th generation cephalosporins?

A

Includes:
-cefepime
-cefquinome
- Broad spectrum
- Cefquinome is currently unavailable in Europe and UK for veterinary use
- Approval for BRD denied by FDA

RARELY USED IN VETERINARY MEDICINE (US) IN ANY SPECIES

21
Q

What are the drugs to know Cephalosporins?

A

1st generation:
-CephAlexin
-CefAzolin

3rd generation:
-Ceftiofur
-Cefpodoxime proxetil
-Cefovecin

22
Q

What are the 1st generation you need to know for Cephalosporins?

A

Cephalexin

Cefazolin

23
Q

What are the 3rd generation you need to know for Cephalosporins?

A

Ceftiofur

Cefpodozime proxetil

Cefovecin

24
Q

What species use Cephalexin?

A

dogs and cats

ORAL

25
Q

How is Cephalexin used?

A

Orally for dogs and cats

FDA approved: Rilexene (chewable) $$$

Dermatitis cause by non-methicillin/oxacillin resistant staphylococci

26
Q

What species use Cefazolin?

A

IV for dogs, cats, and SOMETIMES horses

27
Q

How is Cefazolin used?

A

IV use

Extralabel use

Surgical prophylaxis
-administer within 60minutes of incision
-dose q90-120 minutes until wound closure

28
Q

What is the species you use Cefpodoxime proxetil for?

A

Dogs

29
Q

Cefpodoxime proxetil is prescribed for dogs but has been used safely in what other species?

A

Cats
Foals

30
Q

What is Cefpodoxime proxetil used for?

A

Use in dogs (cats/foals)
-Skin and soft tissue infections

Longer half-life
-once daily dose
-better for owner compliance

PRODRUG
-ester improves oral absorption

31
Q

What species use Cefovecin?

A

dogs and CATS

2# antibacterial in cats

32
Q

What uses does Cefovecin have?

A

FDA approved treatment for skin infections in dogs and cats (convenia)

single SQ dose

Therapeutic for 2 weeks

Long half-life due to affinity protein binding!

33
Q

What important to consider about long lasting antibiotics?

A

Once administered there is NO turning back

Effects persist longer (meaning ADVERSE effects too)

NOT fast acting

34
Q

What species is Ceftiofur for?

A

FDA approved for
(dogs)
horses
chickens
turkeys
cattle
goats
sheep
swine

35
Q

What is Cephalosporins used for?

A

Main Cephalosporin used systemically in LARGE ANIMALS

respiratory issues and foot rot

36
Q

How many formulations does Ceftiofur have?

A

3 formulations:

Ceftiofur sodium (Naxcel)

Ceftiofur hydrochloride (Excenel)

Ceftiofur crystalline free acid (Excede)

37
Q

How do you use Ceftiofur crystalline free acid?

A

Cattle
-single SQ dose at the base of ear

Swine
-single IM dose

Horses
-IM does and REPEATED once in 4 days

38
Q

What is the extralabel use of Cephalosporins in food animals?

A

Prohibited by FDA in major food producing species
-Cattle
-Swine
-Chickens
-Turkeys
EXCEPTION: Cephaphrin

NOT prohibited in minor food producing species
-Sheep
-Goat
-Honeybees
-Fish
-Wildlife

39
Q

What are adverse effects of beta-lactam antibiotics?

A

They are RELATIVELY RARE

-hypersensitivity reactions (anaphylaxis, IMHA)
- cross-reactivity between penicillins and cephalosporins may exist (15% of people)

-VERY high concentrations, can inhibit GABA
- cause CNS excitement and seizures
- can occur with other beta-lactams as well

-procaine reactions (NOT penicillin)

-GI effects
- dogs/cats
–> vomiting oral high dosages
- horses and rabbits
- high incidence of colitis with oral admin

40
Q

Drug interactions with beta-lactam antibiotics

A

Aminoglysoides
-SYNERGISM

-INACTIVATION
- chemical inactivation when mixed (do NOT precipitate)
- Does NOT happen in vivo (diluted by plasma)

41
Q

What are the mechanisms of resistance for beta-lactam antibiotics?

A

1 ENZYME MEDIATED DEGRADATION

Methicillin-resistance
-mediated via the MecA gene
- encodes for penicillin binding protein 2a (VERY low binding affinity for all beta-lactam antibiotics)
-RESISTANT TO ALL BETA-LACTAMS
- includes carbapenems and monobactams

Reduced penetration of drug into bacteria
-gram- capsule
-altered or reduced number of porins
- channels the antibiotics can use to cross cell membranes

-bet-lactamases
-penicillinases
-cephalosporinases
-carbapenemases (BAD)
-other

42
Q

What are the beta-lactamase inhibitors?

A

Clauvulanic acid

Sulbactam

Tazobactam

43
Q

What is the mechanism of action for beta-lactamase inhibitors?

A

Combine with beta-lactanmase enzymes to form an inactive coplex
- gram- and gram+ bacteria

Co-administed antibiotics is then able to exert its effect

Also bind to different PBPs
- bactericidal effects
- NOT sufficient to ever administer ALONE

44
Q

What are formulations combined with a beta-lactamase inhibitor?

A

Amoxicillin + clavulanic acid (Clavamox)

Ampicillin + sulbactam (NOT absorbed orally) (Unasyn)

Ticarcillin + clavulanic acid (Timentin)

Piperacillin + tazobactam (Zosyn)

45
Q

KEY CONCEPT
Beta-lactams are what?

A

Time dependent

Bactericidal

Cell wall inhibitors

RENAL ELIMINATION

Hydrophilic (confined to plasma and ISF)

Synergistic when combined with aminoglycosides

SAFE! Hypersensitivity and mild GI

Some inactivated by beta-lactamases (unless combined with beta-lactamase inhibitors)
ALL INACTIVATED BY
MecA methicillin resistance

46
Q

KEY CONCEPTS

Penicillin G

A

Streptococci and anaerobes

Susceptible to beta-lactamases

Inadvertent IV injection of procaine penicillin causes severe procaine reaction

Benazathine formulations do NOT reach therapeutic concentrations

47
Q

KEY CONCEPTS

Aminopenicillins

A

Steptococci and anaerobes

Increasing gram- spectrum

Susceptible to beta-lactamases unless combined with a beta-lactamse inhibitor
-amoxicillin + clavulanic acid
- ampicillin + sulbactam

Amoxicillin + clavulanic acid (CLAVAMOX) =
#1 antibiotic to DOGS
#2 antibiotic to CATS

48
Q
A

DWT Exam 2 (21 decks)

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