Polymyxins Flashcards

1
Q

Pharmacokinetics:

A

Absorption: Poor- not oral or topical.

Distribution: Poor- blood plasma is low because polymyxins bind to cell membranes as well as tissue debris and purulent exudates.

Metabolism:

Excretion: Kidney. T1/2 3-6 h.

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2
Q

Mode of action:

A

Bactericidal.

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3
Q

Mechanism of action:

A

Disrupt cell membrane (LPS) and disrupt the function and permeability.
Works on gram-.

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4
Q

Spectrum:

A

Gram- bacilli.
Enterobacter, Klebsiella, Salmonella, Pastuerella, Bordetella, Shigella, E.Coli, Pseudomonas.

Topical: S. aureus.

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5
Q

Chemistry:

A

Is a positive charge= attracted to -.
(Gram+ have thick wall and no outer membrane= don’t work.)

Polymyxins neutralize LPS.

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6
Q

In case of E.coli:

A

Polymyxins kills E.coli fast -> endotoxins released -> endotoxaemia, that can kill!
Piglets are especially sensitive.

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7
Q

Most used polymyxin in vet. med:

A

Polymyxin B, polymycin E= colistin
Polymyxin M

Used topically or PO.

Colistimethate is a form of colistin- parenteral admin.

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8
Q

Polymyxin B:

A

Topical ointment in mixture with bacitracin or neomycin.

Synergistically when combined with: potentiated sulfonamides, tetracyclines, and penicillins, fluoroquinolones, aminoglycosides.

POTENT HISTAMINE RELEASER!

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9
Q

Resistance:

A

Uncommon. <5%.

Chromosomal, plasmid encoded?

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10
Q

Side effects:

A

Nephrotoxic -> tubular necrosis.
Neurotoxic.
Used mainly oral, opthalmic, otic or topical because of this.
Higher cc -> neuromuscular blockade.
Pain at injection site.
Polymyxin is a potent histamine releaser.

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11
Q

Polymyxin Indication:

A

Parenteral: Lifethreatening infection gr-. Pseudomonas.
WP= 0 days. IV can be potentially toxic.

Oral: intestinal infection.

Topical: pyoderma, otitis extrena, intramammary,

Colistin: gr- mastitis in cow, endotoxins can kill cow fast.

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