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General Pharmacology 2 > Antimicrobial Therapy: Aminoglycosides, Aminocyclitols, and Fluoroquinolones > Flashcards

Antimicrobial Therapy: Aminoglycosides, Aminocyclitols, and Fluoroquinolones Flashcards

1
Q

Aminoglycosides

A

originally isolated form Streptomyces or Mircomonospora

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2
Q

Aminoglycosides:

Spectrum

A

Gram negative aerobes, some gram positive, NOT streptococcus, NOT anaerobes

Oxygen dependent pathway for bacterial uptake

Pseudomonas - YES

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3
Q

Aminoglycosides:

Concentration

A

Peak dependent, rapidly bactericidal

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4
Q

Aminoglycosides:

Elimination

A

Renal

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5
Q

Aminoglycosides:

Use

A

parenteral only for systemic effects

Often incorporated into topical medications

Oral aminoglycoside only are effective to treat enteric bacteria

Intra-articular, intravenous regional perfusion ot treat joints

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6
Q

Aminoglycosides:

MOA

A

30s ribosomal inhibitor

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7
Q

Aminoglycosides:

Conditions decreaseing Efficacy

A

Needs active uptake due to hydrophilicity

Cellular debris, low pH anaerobic conditions decrease bacterial uptake and efficacy

Can be inactivated in vitro by mixing with other antimicrobials, especially beta lactams

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8
Q

Aminoglycosides:

Distribution

A

excluded from protected environments

Vd larger in neonates = increased doses compared to adults

Low plasma protein binding

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9
Q

Aminoglycosides:

Resistance

A

inactivating enzymes

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10
Q

Aminoglycosides:

Toxicity

A
  • Renal, otic, could enhance neuromuscular blockade of neuromuscular blockers
    • renal toxicity may be reversible if caught early; prior to basement membrane loss of tubules
      • renal tubular casts appear first
      • If azotemia develops, too late, nephrons lost, will get worse
      • Therapeutic Drug monitoring and icrease in half-life is the best indicator of renal toxicity
  • Minimization of Toxicity
    • only administer to hydrated animals
    • Drug free intervals
    • Minimize duration of therapy
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11
Q

Aminoglycosides:

Gentamicin

A
  • IV, IM, SQ, Intra-articular, Intravenouse regional perfusion and Topicals
  • Is actually a mixture of 3 active components, but expressed as a sum on the label
  • They are essentially equally active and toxic
    • once daily to maximize efficacy / minimize toxicity
    • Most commonly used in horses systemically
    • Do not administer intra-abdomen for peritonitis
    • Intramammary administration results in systemic absorption and violative residues
    • Commonly included in otic/opthalmic traetments
    • Oral administration results in little systemic absorption
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12
Q

Aminoglycosides:

Amikacin

A

Same as gentamicin except less susceptible to inactivating enzymes

Therefore you can have a gentamicin resistanct, amikacin susceptible bacteria

No Substantial difference in nephrotoxicity risk

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13
Q

Aminoglycosides:

Neomycin

A

oral/topical ONLY

PO administration only for enteric infections

With enteritis some drug will be asborded systemically

Labels for food animal use (PO only)

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14
Q

Aminocyclitols:

Spectinomycin

A

Similar to aminoglycosides, BUT

  • not nephrotoxic
  • Bacteriostatic
  • Less active agianst gram negative
  • No efficacy for Pseudomonas
  • Effective for Mycoplasma, but many other drugs are too

Poor PO bioavailability

Hydrophilic, does not penetrate protected tissues well

Injection no longer available

DO NOT COMPOUND INJECTION FROM SPECTINOMYCIN POWDER

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15
Q

Fluoroquinolones

A

Synthetic antimicrobials, not naturally occurring

Spectrum very similar to aminoglycosides

Gram negative aerobes, Pseudomonas, Staphylococcus, Most also have activity against Brucella, Chlamydophila, Rickettsia, +/- mycoplasma

Essentially no Streptococcus and no anaerobes

Newer FQs added anaerobes, and Streptococcus

Rapidly bactericidal, concentration dependent

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16
Q

Fluoroquinolones:

Absorption

A

PO yes,

Also IV, IM, SQ topical

17
Q

Fluoroquinolones:

Distribution

A

widely distributed including protected environments

18
Q

Fluoroquinolones:

Metabolism

A

most species vairable metabolize enrofloxacin to ciprofoxacin contributing to its activity

19
Q

Fluoroquinolones:

Elimination

A

most elimination by renal mechanisms, marbofloxacin mixed

20
Q

Fluoroquinolones:

Pharmacokinetic Interactions

A

most chelate to di- and trivalent cations and cause inactivation

Enrofloxacin appears to be the exception with similar PK with concurrent sucralfate - not assessed with other drugs

Most FQs inhibit some CYP.

Major interaction is with theophyline

21
Q

Fluoroquinolones:

Mechanism

A

Bacterial Topoisomerase inhibition

DNA gyrase: introduces negative supercoiling

Topoisomerase: IV, also allows DNA to uncoil

22
Q

Fluoroquinolones:

Resistance

A
  • No mutaiton = normal
  • 1 step topoisomerase 2 mutation:
    • MIC increase, but still may be effective dose if appropriate drug/dose used
  • 2 step also topoisomerase 4 mutation
    • MIC increased further = complete resistance
23
Q

Fluoroquinolones:

Adverse Effects

A
  • In general, well tolerated
  • High doses/concentrations can cuase CNS toxicity and seizures
    • avoid in patients prone to seizures
  • Young growing animals are susceptible to cartilage damage which can result in permanent damage
    • foals and young growing large breed dogs are susceptible
  • Retinal toxicity and blindness reported in cats with high doses / concentrations
  • Rarely vomiting / diarrhea with high doses
  • In humans, tendon injuries are reported
24
Q

Fluoroquinolones:

Vet label:

Enrofloxacin

A

dogs, cats, cattle (including non-lactating dairy), swine

25
Q

Fluoroquinolones:

Vet Label:

Orbifloxacin

A

dogs and cats

26
Q

Fluoroquinolones:

Vet Label:

Marbofloxacin

A

dogs and cats

Extra label: for cattle, horses

27
Q

Fluoroquinolones:

Vet Label:

Danofloxacin

A

cattle

28
Q

Fluoroquinolones:

Vet Label:

Pradofloxacin

A

cats

29
Q

Fluoroquinolones:

Human Label:

Ciprofoxacin

A

not ideal ….

30
Q

Fluoroquinolones:

Human Label:

Levofloxacin

A

humans

31
Q

Food Animal Use

A

Enrofloxacin:

Cattle for respiratory disease

Swine for respiratory disease and colibacillosis

Danofloxacin:

Cattle not intended for dairy or veal for respiratory disease

NO EXTRALABEL DRUG USE IN FOOD ANIMALS

32
Q

Enrofloxacin

A
  • Small animal injection, tabs, chewables
  • Food animal injection
  • Generics available
  • Enrofloxacin injection may percipitate in IV fluid line if not diluted
  • Large animal formulation is basic and can cause tissue damage,
    • in horses, causes mucosal damage when administered PO.
    • Sterile abscesses in dogs and cats occur regularly
  • Once daily administration for small animlas, horses.
    • Cattle can also be administered a single high dose
    • Swine administered a single dose
  • ELDU in food animals is prohibited
  • Human ingestion can result in sever neurologic adverse effects
33
Q

Marbofloxacin

A
  • Available as tablets, once daily admin.
  • Mixed hepatic/renal elimination - no need to dose adjust with renal failure
  • May be less likely to cause blindness in cats
  • Often has greater activity than other FQs against many gram negative and Pseudomonas
    • often 1 fold dilution lower
    • Therefore some infections may be treated successfully with marbofloxacin, but not enrofloxacin
  • Has a better pharmacokinetic profile than enrofloxacin
34
Q

Orbifloxacin

A

liquid and tablet formulations

Approved for dogs and cats, once daily admin.

Similar to other FQs

Overall lower activity vs. other FQs

35
Q

Pradofloxacin

A

Approved for cats (suspension)

Enhance spectrum against Streptococcus and anaerobes

Used for dental infections

Otherwise similar to other FQs

36
Q

Danafloxacin

A

approved for use in cattle with respiratory disease

No advantages/disadvantages compared to enrofloxacin, except indications

Can be administered as a single injection or split inot q48h injections for 2 doses total

37
Q

Ciprofloxacin

A
  • Approved for use in humans only, extralabel use allowed in non-food animals
  • Poor oral bioavailability in most species
  • Vary variable in dogs
    • inconsistent absorption linits its effectiveness to only highly susceptible bacteria, results in essentially 10x lower potency compared to enrofloxacin
    • Ciprofloxacin generic breakpoint for susceptible
    • Enrofloxacin breakpoint is 0.5mcg/ml
    • Only reason it is used is because of its low cost, otherwise inferior to other FQs
38
Q

Levofloxacin

A
  • Human approved, extra label use allowed in non-food animals
    • available as tablets and injection
    • Primarily used orally in veterinary medicine
  • Enhanced spectrum agianst gram positive and anaerobes similar to pradofloxacin
  • Otherwise is similar to other FQs
  • Good oral bioavailability in dogs and cats
  • A generic breakpoint of 0.5mcg/ml for Enterobacteriacease adn 1mcg/ml for Pseudomonas
    • pradofloxacin can be used as a surrogate marker on cultures
    • remember cirpofolxacin generic breakpoint

General Pharmacology 2 (17 decks)

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