Chapter 4 – Carbadox (quinoxalines)


Carbadox is the only representative of the quinoxaline family that is commonly used in swine. It is used to control post-weaning colibacillosis and was added to the feed as a growth promoter. Carbadox is mainly fed to nursery age pigs because of its long withdrawal time. It is banned in countries other than the USA because of its carcinogenic effects. Information on carbadox pharmacokinetics is limited.

Useful molecules to know in swine medicine:

  • Carbadox

Mechanism of Action

Carbadox inhibits DNA synthesis and can also break DNA existing DNA and has a bactericidal effect.


Carbadox is most effective against Gram + bacteria and in anaerobic conditions. It is highly active against Clostridium spp. and Brachyspira spp.


No reliable information was found on carbadox absorption.


The volume distribution of cardabox is fair.


More than 50% of carbadox metabolites are excreted in the urine. The half-life is relatively short, around 6 hours.

Adverse effects

Metabolites of carbadox have been shown to be carcinogenic. Therefore, carbadox use in food animal species is prohibited in countries such as Canada and the European Union.

In the USA, withdrawal time for carbadox is 42 days, therefore its use is limited to younger pigs in the nursery.


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

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