Chapter 6 – Ionophores


Narasin is the ionophore most largely used in swine medicine. It is mainly used as a growth promotant and is not under the Veterinary Feed Directive.

Useful molecules to know in swine medicine:

  • Narasin

Mechanism of Action

Ionophores alter the permeability of the bacterial cell membrane and increasing the passive release of potassium from the bacteria. Ultimately, the fragile osmosis equilibrium is disrupted, the pH decreases and the bacteria ultimately dies.

Check your learning: Ionophores and mechanism of action


Gram + bacteria tend to be more susceptible to ionophores than Gram –


Ionophores are largely absorbed after the administration per os.


They do not accumulate in the tissues and are therefore more adapted to the control of the intestinal flora.


Ionophores are metabolized in the liver and are majoritarily excreted in the bile and then in the feces.

Adverse effects

Ionophores should not be given at the same time as pleuromutilins such as tiamulin.


Swine Antibiotherapy Handbook Copyright © by Perle Zhitnitskiy. All Rights Reserved.

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