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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
How is Cephalexin used?
Orally for dogs and cats FDA approved: Rilexene (chewable) $$$ Dermatitis cause by non-methicillin/oxacillin resistant staphylococci
26
What species use Cefazolin?
IV for dogs, cats, and SOMETIMES horses
27
How is Cefazolin used?
IV use Extralabel use Surgical prophylaxis -administer within 60minutes of incision -dose q90-120 minutes until wound closure
28
What is the species you use Cefpodoxime proxetil for?
Dogs
29
Cefpodoxime proxetil is prescribed for dogs but has been used safely in what other species?
Cats Foals
30
What is Cefpodoxime proxetil used for?
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
What species use Cefovecin?
dogs and CATS 2# antibacterial in cats
32
What uses does Cefovecin have?
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
What important to consider about long lasting antibiotics?
Once administered there is NO turning back Effects persist longer (meaning ADVERSE effects too) NOT fast acting
34
What species is Ceftiofur for?
FDA approved for (dogs) horses chickens turkeys cattle goats sheep swine
35
What is Cephalosporins used for?
Main Cephalosporin used systemically in LARGE ANIMALS respiratory issues and foot rot
36
How many formulations does Ceftiofur have?
3 formulations: Ceftiofur sodium (Naxcel) Ceftiofur hydrochloride (Excenel) Ceftiofur crystalline free acid (Excede)
37
How do you use Ceftiofur crystalline free acid?
Cattle -single SQ dose at the base of ear Swine -single IM dose Horses -IM does and REPEATED once in 4 days
38
What is the extralabel use of Cephalosporins in food animals?
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
What are adverse effects of beta-lactam antibiotics?
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
Drug interactions with beta-lactam antibiotics
Aminoglysoides -SYNERGISM -INACTIVATION - chemical inactivation when mixed (do NOT precipitate) - Does NOT happen in vivo (diluted by plasma)
41
What are the mechanisms of resistance for beta-lactam antibiotics?
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 #1 ENZYME MEDIATED DEGRADATION -bet-lactamases -penicillinases -cephalosporinases -carbapenemases (BAD) -other
42
What are the beta-lactamase inhibitors?
Clauvulanic acid Sulbactam Tazobactam
43
What is the mechanism of action for beta-lactamase inhibitors?
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
What are formulations combined with a beta-lactamase inhibitor?
Amoxicillin + clavulanic acid (**Clavamox**) Ampicillin + sulbactam (NOT absorbed orally) (*Unasyn*) Ticarcillin + clavulanic acid (*Timentin*) Piperacillin + tazobactam (*Zosyn*)
45
KEY CONCEPT Beta-lactams are what?
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
KEY CONCEPTS Penicillin G
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
KEY CONCEPTS Aminopenicillins
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

DWT Exam 2 (21 decks)

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