Imidazothiazole (levamisole or ‘clear’)

What does it treat?


Note:  Levamisole is dangerous to fish. Do not contaminate streams, rivers or waterways with the product or with used containers.

How is it administered?

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

Oral  Pour-on

  • Injectable products are registered in other countries and may become available in the future.

Warning:  Ensure that treated animals are not dehydrated and have free access to water following dosage according to their weight band.

                 Check the label for other warnings


Reported in:  Roundworm

Resistance to levamisole in Australia is fairly widespread for the small brown stomach worm (Ostertagia ostertagi).

What is resistance?


  • Read the product label for any restrictions and exercise care with weak or pregnant animals to avoid unnecessary stress.

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


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

  • 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.

Types of imidazothiazole

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. Imidazothiazole, 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)









Intestinal tapeworm

Liver fluke





Combination (all actives target boxed parasite)


Levamisole and abamectin


Levamisole and moxidectin







Levamisole, abamectin and oxfendazole


Mixtures (multiple targets)


Levamisole and oxyclozanide



What is it?

Levamisole is a synthetic compound that was discovered in the 1960s and has been used as an anthelminthic treatment for cattle and other animals since then. It is a member of a larger group of compounds called Imidazothiazoles. Levamisole provides broad-spectrum anthelmintic activity against roundworms (nematodes) with no activity against flukes or tapeworms. It is not ovicidal which means levamisole does not kill parasite eggs. It also has limited activity against tissue stages (encysted) small brown stomach worms (Ostertagia ostertagi).

How does it work?

The mode of action of Imidazothiazoles is to continually stimulate the nicotinic acetylcholine receptors within the body wall muscles of nematodes, causing spastic paralysis of the worm, and expulsion from the host.