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1

Choice of AB is determined by

  • susceptibility of bacteria
    • main target is staph
  • concurrent dz
  • depth of infection
  • length of tx
  • breed
  • age
  • owner constraints

2

General rules for antibiotic therapy

  1. Select AB with narrow spectrum
  2. Select AB with wider margin of safety
  3. Try to never combine AB with glucocorticoids

3

AB for pyo

First line

  1. Erythromycin
  2. Lincomycin
  3. Clindomycin
  4. First gen cephalosporines

4

AB for pyo

Second line

  1. potentiated sulfonamides
  2. third gen cephalosporins
  3. amoxicillin/clavulanic acid

5

AB for pyo

Third line (Big guns)

  1. Fluoroquinalones
  2. Chloramphenicol
  3. Rifampin
  4. Amikacin

6

Erythromicin

  1. Macrolide; inhibits ribosomal protein synthesis
  2. Bacteriostatic, Time-dependent (TID)
  3. Narrow spectrum for staph
  4. Vomiting almost a given
  5. Inhibits cytochrome P450
  6. absorption delayed by food administration (inactivated by gastric secretions)

7

Lincomycin

  1. Macrolide-like AB
  2. Bacteriostatic, admin BID
  3. better absorption/distribution, less vomiting than erythromycin
  4. rapid resistance

8

Clindamycin

  1. Related to lincomycin, BID
  2. Absorption not altered by food
  3. Good penetration in fibrotic tissues
  4. Skin infection dose 11 mg/kg
  5. high effectiveness treating methicillin resistent staph
  6. Well tolerated by most, used frequently for S. schleiferi
    • nosocomial infections in people and dogs

9

Cephalosporins

  • Broad spectrum bacteriacidal
    • inhibits synthesis of bacterial cell wall

10

Cephalexin

  1. First generation cephalosporin, broad spectrum but mostly Gram +
  2. Adverse affects
    • GI
    • Immune mediated disease

11

Details about second line choices

  1. Potentiated sulfonamides
  2. Third generation cephalosporins
    • broader spectrum good for mixed infections
  3. Amoxicillin/clavulanic acid
    • will not work for s. pseudointermedius

12

Can't use clavamox if an infection is ...

methicillin resistent

13

Potentiated sulfonamides

  1. Interfere with synthesis of folic acid
  2. Immunogenic - triggers hypersensitivity
    • type I: IgE mediated (swollen, red)
    • type II: cytotoxic (Immune mediated thrombocytopenia)
    • type III: immune complex deposition (lupus)
  3. Antacids interfere with absorption

14

Shifting leg lameness

can be adverse affect of sulfas

15

Potentiated sulfonamides

Adverse affects

  • Anemia, leukopenia, thrombocytopenia
  • KCS
  • shifting leg lameness (lupus-like joint symptoms)
  • hypothyroidism

16

Two drugs that will affect thyroid levels

  • Pred
  • Sulfas

17

Dogs that should not see sulfas

  • Black and tan dogs: arthropathy
    • Dobies
    • Rotties

18

Silver sulphadiazine

  • topical sulfonamide
  • broad spectrum
  • ideal for Pseudomonas
  • ears and skin

19

Cefovecin (Convenia)

Defpodoxime proxetil (Simplicef)

Third gen cephalosporins

  • broader spectrum, active against G-
  • activity against s. pseudointermedius same as first gen
  • potential selection for methicillin resistence
  • Use as a first choice if compliance might be a problem (injectible)

20

Beta-lactamase resistant penicillins

  • Oxacillin
  • Dicloxacillin
  • Nafcillin
  • Expensive
  • Excellent for staph
  • TID

21

Amoxicillin/Clavulanic acid

(Clavamox)

  • Broad spectrum: primarily Gram +
  • Bacteriocidal
  • Rapid absorption
  • GI side effects
  • Dose: 22 mg/kg BID
  • Expensive for big dogs

22

Chloramphenicol

  • Broad spectrum, inhibits ribosomal protein synthesis, bacteriostatic
  • Time-dependent 50 mg/kg TID
  • metabolized by the liver
  • Owners: aplastic anemia 
  • anemia in animals is reversal
  • peripheral neuropathy in large breed dogs

23

Fluoroquinalones (Baytril)

  • only use in resistant cases as last resort
  • Concentration dependant (use once daily high dose)
  • Absorption inhibited by antacids
  • Great for deep pyo
  • GI, Nuero signs
    • lowers threshold for seizures

24

Enrofloxacin (Baytril)

Fluoroquinalone

  • bioconverted to cirpofloxacin
  • Bioavailability: 40%
  • 20 mg/kg once a day
  • expensive

25

Marbofloxacin (Zeniquin)

Fluoroquinalone

  • Bioavailability: 94%
  • Dose: 2.75 - 5.5 mg/kg SID

26

Orbifloxacin (Orbax)

Fluoroquinalone

  • Bioavailability: 97%
  • Dose: 2.5 mg/kg SID

27

Moxifloxacin

  • human product
  • used in dogs at 8 mg/kg SID

28

Pradofloxacin (Veraflox)

  • 3rd gen enhanced spectrum vet fluoroquinalone
  • Europe: labeled for dogs; US: labeled for cats
  • b/c baytril can't be used for cats
  • extensive ocular safety testing

29

bioavailability of cipro versus enrofloxacin

enrofloxacin has a more consistent bioavailability

30

Doxycycline

  • Time dependent antibiotic: 5-10 mg/kg BID
  • used for resistent cases
  • very expensive, substituted with minocycline
  • anti-inflammatory properties
  • adverse affects
    • GI
    • yellow staining of teeth
    • esophageal strictures