Sulfonamide (SF Clorsulon)

What does it treat?

 Liver fluke

  • Clorsulon is no longer available in Australia as a single active but it is sold as a mixture with ivermectin, or a combination with nitroxynil.

How can they be administered?

A variety of application methods for administering pesticide products to cattle are in use.


  • Spillage at injection site may stain lighter coats


Resistance of liver fluke to clorsulon not reported in Australia.

What is resistance?


  • Clorsulon is generally regarded as a compound of low-toxicity but it can cause eye and skin irritation in some people.

Everyone working in the rural industry has a ‘duty of care’; a legal obligation to provide a safe workplace for everyone on the property.


  • Always check the product label before use for specific withholding periods (WHP) and export slaughter interval (ESI) periods. Current ESI periods can be confirmed on the APVMA website.

Withholding periods are mandatory with all registered veterinary products used to treat animals for internal and external parasites.

Types of sulfonamide

A guide to the different actives and the pests they affect are in Table 1. See the Products Search Guides for WormBoss, TickBoss, LiceBoss and FlyBoss for the appropriate formulation and application method for your target pest. Note combinations and mixtures of actives may improve treatment efficacy.

Table 1. Sulfonamide, their active, combinations and mixtures and a summary of the targeted parasites for which formulations are registered for. Boxed check marks indicate the pest targeted by multiple actives.


Pests targeted (may vary with formulation)



Cattle tick


Chorioptic mange mite


Tape worm

Liver fluke






Combination (all actives target boxed parasite)


Clorsulon and nitroxynil



Mixtures (multiple targets)


Clorsulon and ivermectin



Mixtures and combinations (multiple targets, primary target of actives boxed)


Clorsulon, nitroxynil and ivermectin



What are they?

Sulfonamides (SFs) are synthetic chemicals.

How do they work?

Clorsulon is a narrow-spectrum anti-parasitic. Clorsulon inhibits enzymes involved in the glycolytic pathway, the primary source of energy in liver flukes.