Combination-Drench Efficacy Calculator


Enter your drench efficacy (%) results in the fields below. Where you have no data, leave the field empty.

Single actives Barber's pole worm Black scour worm Brown stomach worm
BZ (albendazole, fenbendazole or oxfendazole)
Abamectin and derquantel**
Levamisole and oxyclozanide**


The data (above) for single-actives will be used to predict % efficacy of combinations (below). ‡ Blank result cells indicate insufficent data to calculate a prediction.

Predicted efficacy (%) of combination drenches Barber's pole worm Black scour worm Brown stomach worm
BZ and levamisole
BZ and naphthalophos
BZ and closantel***
BZ and abamectin
Abamectin and levamisole
Abamectin and closantel***
Naphthalophos and levamisole
Naphthalophos and abamectin
Naphthalophos and moxidectin
BZ and levamisole and naphthalophos
BZ and levamisole and ivermectin
BZ and levamisole and abamectin
BZ and levamisole and moxidectin
BZ and levamisole and praziquantel
BZ and abamectin and closantel and levamisole

*Closantel. Bear in mind that the amount of closantel per dose is not the same for all products containing closantel, so results of efficacy testing (and predictions based on these results) can vary between products, even if the label dose rate is used.

**Derquantel and oxyclozanide do not come in single active formulations.

*** For barber's pole worm, these products act as combinations, but for black scour and brown stomach worm they act as mixtures because closantel does not control these worm types.

‡ There are other drench products with two actives that are not listed here because they are mixtures, not combinations. These include either triclabendazole (which targets liver fluke) or praziquantel (which targets tapeworm). With such mixtures, only one of their actives works against roundworms. Therefore, the efficacy of these mixtures against roundworms is the same as their single-active component for roundworm.

Testing systems are very useful, but imperfect. When combined with biological systems, test results provide approximations and may vary from one test to another.  For this and other reasons, WormBoss recommends regular DrenchChecks in between 2–3 yearly DrenchTests.

Future events cannot reliably be predicted accurately. Sheep CRC Ltd (“Sheep CRC”), The University of New England (“UNE”), Australian Wool Innovation Limited (“AWI”) and Meat & Livestock Australia Limited (“MLA”) make no statement, representations or warranties about the accuracy or completeness of, and you should not rely on any information relating to the WormBoss Worm Control Program (“Information”). Sheep CRC, UNE, AWI and MLA disclaim all responsibility for the Information and all liability (including without limitation liability for negligence) for all expenses, costs, losses and damages you may incur as a result of the Information being inaccurate or incomplete in any way for any reason. Published December 2015 © Sheep CRC Ltd, The University of New England, Australian Wool Innovation Limited and Meat & Livestock Australia Limited 2015.

Downloadable file:

More information:

What are the benefits of combination drenches?
What is the difference between a combination and a mixture?