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Pharmacology > Phenicols > Flashcards

Phenicols Flashcards

1
Q

Phenicols

A

-includes florfenicol and chloramphenicol
-have different side chains

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2
Q

Florfenicol

A

-used for both food animal products and companion animal products

-includes Nuflor, Resflor, Zeleris, Aquaflor, Osurnia,Claro

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3
Q

Nuflor

A

-florfenicol
-injectable solution
*cattle (IM/SC) used for resp disease, footrot, pinkeye
*swine (IM) used for resp disease

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4
Q

Resflor

A

-florfenicol +flunixin (NSAID) injectable solution
-administer SC
-used for resp disease and pyrexia in cattle

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5
Q

Zeleris

A

-florfenicol +meloxicam
-injectable solution (SC)
-used for resp disease and pyrexia in cattle

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6
Q

Aquaflor

A

-medicated premix for salmon
-used for Aeromonas and Vibrio infections

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7
Q

Osurnia, Claro

A

-Florfenicol WITH terbinafine (Antifungal) and betamethasone or mometasone (steroid)

-once per week ear med

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8
Q

Chloramphenicol

A

-not a first line drug but nice to have as a reserve

-includes Chlor Palm 250/Chlor-palmitate
-also have human generic formulations

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9
Q

Chlor Palm 250, Chlor-palmitate

A

-chloramphenicol
-oral suspensions (chalky)
-used for various infections in small dogs and cats

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10
Q

Human generic formulations of Chloramphenicol

A

-oral tablets and suspension
-injectable (sodium succinate solutions)

**better for larger dogs because can give a pill instead of the chalky solutions

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11
Q

Phenicols mechanism of action

A

Binds to bacterial ribosomal 50S subunit
-causes incorrect tRNA translation and disrupts bacterial protein synthesis

BUT also inhibits mitochondrial protein synthesis

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12
Q

Phenicols impact on mitochondria

A

Inhibits mitochondrial protein synthesis in mammalian bone marrow
*impacts blood cell production
*dose-dependent effect

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13
Q

Phenicols spectrum of activity

A
  1. many gram +
    *includes MRSA/P
  2. many gram -
  3. many anaerobes
  4. Some mycoplasma
    *in vitro
  5. Some Rickettsia and chlamydia
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14
Q

What are phenicols not effective against?

A
  1. Gram negative enterics (often resistant to chloramphenicol, less to florfenicol)
  2. Pseudomonas
  3. Enterococcus
  4. Rhodococcus, Mycobacterium, Nocardia

**Resistance emerges fast in many bacterial species!!!

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15
Q

Enterococcus and E coli MICs with phenicols

A

Often high MIC
BUT clinical success has been observed in many cases

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16
Q

Ways that the bacteria can become resistant to phenicols

A
  1. enzymes add acetyp group
  2. decrease phenicol permeability
  3. increase efflux pumps
  4. mutations to 50S binding sites
  5. Resistance genes are often mobile= plasmids and transposons
17
Q

Enzymes adding acetyl group= resistance

A

Chlorampheicol acetrltransferases (CATs) prevent the binding to ribosome 50S subunit

**FLOR less vulnerable to acetylation

18
Q

Chloramphenicol bioavailability

A

-overall good
-may be higher in cats in fed state
-inactivated in the rumen but not a huge issue

19
Q

Florfenicol bioavailability

A

-prolonged absorption after IM/SC injection

-does undergo flip-flop kinetics
**long acting, slowly absorbed from injection

20
Q

Flip flop kinetics

A

Flatter slope= slower rate of elimination
*absorption still occurring during elimination phase

21
Q

Distribution of phenicols

A

-moderate/high Vd (~1L/kg)

-can cross placenta

22
Q

Elimination of phenicols

A

Hepatic metabolism and glucuronide conjugation
*poor in cats so longer half life and dosing interval
*much longer half life in young animals
*can have drug reactions with other drugs being metabolized in the liver

Renal excretion of inactive metabolites (so no need to worry about renal failure)

23
Q

Phenicols are bacteriostatic

A

-difficult to reach MBC

-considered time dependent
*more frequent dosing may be of benefit
*recommended T>MIC for more than 50% of dosing interval

24
Q

Phenicol administration with other antibiotics

A

Not recommended. They can be antagonistic with other antibiotics
*beta lactams, macrolides, aminoglycosides, fluoroquinolones

25
Q

Chloramphenicol hepatic metabolism interactions

A

Microsomal enzyme inhibitors (CYP)
-can prolong barbituate anesthesia
-inhibit metabolism of phenobarb and other CYP mediated drugs

26
Q

Does Florfenicol cause hepatic drug interactions?

A

Not known to cause it in food animals
-but we are often not administering multiple antibiotics in food animals at the same time OR looking for any drug interactions

*may see it in companion animals but often not using long terms o likely fine

27
Q

Adverse blood event for phenicols

A

Blood dyscrasias (aplastic anemia, pancytopenia)
-decreased production of RBC, WBC, platelets

-dose dependent; related to total phenicol exposure (AUC)
**cats more likely to develop toxicity due to increase exposure and decreased clearance =glucoronidation

-dose independent (idiosyncratic) aplastic anemia
*can be fatal to humans (low odds)
*related to para-nitro group on chlorophenicol (not florfenicol)

28
Q

What causes blood dyscrasis from phenicols ?

A

Mitochondrial protein inhibition in bone marrow
*occurs in both animals and humans

29
Q

Chloramphenicol use in food animals

A

BANNED
-avoids idiosyncratic dose independent aplastic anemia in people

30
Q

Adverse GI events from phenicols

A

Chloramphenicol= vomit, diarrhea, inappetence

Florfenicol= change in GI normal flora, diarrhea in calves

31
Q

Chloramphenicol dosing

A

Dogs= 3-4x a day
Cats= 2x a day

Long term administration is not recommended! limit to 10days, if not response in 3-5 days then discontinue

32
Q

Chloramphenicol use against MDR pathogens

A

-not a first line drug but can be used for difficult resistant pathogens

33
Q

Florfenicol in cattle

A

-Nuflor
-label claim for footrot and pink eye BUT not appropriate 1st line choice!!
They are relatively wimpy pathogens and often could just use a penicillin

Pharmacology (37 decks)

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