Brand: STARTECT ® Broad Spectrum Oral Drench

Company: ZOETIS

DELIVERY FORM: «drench» for oral administration.


CHEMICAL CLASS of the active ingredient(s):


PARASITES CONTROLLED (spectrum of activity)



Sheep: 1 ml product/5 kg bw (equivalent to 0.2 mg of abamectin/kg and 2 mg derquantel/kg)

  • ≤15 kg: 3 ml product
  • 16-20 kg: 4 ml product
  • 21-25 kg: 5 ml product
  • 26-30 kg: 6 ml product
  • 31-35 kg: 7 ml product
  • 36-40 kg: 8 ml product
  • 41-45 kg: 9 ml product
  • 46-50 kg: 10 ml product
  • 51-55 kg: 11 ml product
  • 56-60 kg: 12 ml product
  • 61-65 kg: 13 ml product
  • 66-70 kg: 14 ml product
  • 71-75 kg: 15 ml product


  • LD50 (acute oral) in rats:
    • Abamectin: a.i. 10 mg/kg
    • Derquantel: a.i. > 1200 mg/kg
  • LD50 (acute dermal) in rats:
    • Abamectin: a.i. 330 mg/kg
    • Derquantel: a.i. >2000 mg/kg

Suspected poisoningRead the article on abamectin safety in this site.

Withholding periods (=withdrawal times) in days for meat & milk (country-specific differences may apply: read the product label)

  • Meat:
    • UK 14 days; Australia 14 days (ESI = 28 days); NZL 14 days
  • Milk for human consumption:
    • UK & Australia: DO NOT USE in female sheep which are producing or may in the future produce milk or milk products for human consumption
    • NZL: 35 days

WARNING !!!: Never use on humans, dogs and cats

You may be interested in the following articles in this site dealing with the general safety of veterinary products:


Risk of resistance? LOW, resistance of gastrointestinal roundworms to macrocyclic lactones (incl. abamectin) in ruminants is a very serious and increasing problem worldwide, particularly in sheep and goats. The most affected worm species are: Haemonchus spp, Ostertagia spp /Teladorsagia spp, Trichostrongylus spp, Nematodirus spp, Chabertia ovina.

However, derquantel is effective against against Haemonchus spp & Trichostrongylus spp and Ostertagia spp /Teladorsagia spp, resistant to macrocyclic lactonesbenzimidazoles and levamisole. Thus the risk of control failure due to resistance of thes parasites is rather low. Nevertheless, efficacy of derquantel against Ostertagia spp /Teladorsagia spp has been described as variable and <95%. And it has not been reported so far whether derquantel also controls resistant strains of Nematodirus spp and Chabertia ovina.

Altogether it can be said that if this product does not achieve the expected efficacy against the mentioned parasites, it is most likely due to incorrect use, which is usually the most frequent cause of product failure.

Nevertheless, since gastrointestinal roundworms can develop resistance to new active ingredients rather quickly, periodically changing the chemical classes of the anthelmintics used is (so-called rotation) highly recommended.

Alternative chemical classes/active ingredients to prevent resistance of gastrointestinal roundworms through product rotation:

These alternative products may not be available in all countries, or may not be available as drenches, or may not be effective against all the concerned parasites.

It is highly recommended to periodically check the resistance status of each property performing appropriate tests (e.g. fecal egg counts) under supervision of a veterinary doctor. Such tests are now routinely available for most producers in developed countries.

Learn more about resistance and how it develops.


Are the active ingredients of this product ORIGINAL* or GENERICS**?

  • Abamectin: GENERIC
  • Derquantel: ORIGINAL

*Meaning that they are still patent protected and generics are not yet available
**Meaning that they have lost patent protection and may be acquired from manufacturers of generic active ingredients other than the holder of the original patent.

COUNTRIES where this brand/product is marketed: Australia, Ireland, New Zealand, South Africa, UK

Click here to learn more about GENERIC vs. ORIGINAL drugs.

For an overview on the most used drench brands for livestock click here.


STARTECT Broad Spectrum Oral Drench for sheep is the original brand from ZOETIS with derquantel. It contains abamectin to ensure a broader spectrum of activity.

Derquantel shows high efficacy against several gastrointestinal roundworms that affect sheep. At the recommended therapeutic dose derquantel is highly effective against Haemonchus spp, Cooperia spp, and Trichostrongylus spp, including those resistant to most classic anthelmintics (benzimidazoles, levamisole, macrocyclic lactones). However it has a lower and variable efficacy against Ostertagia spp (= Teladorsagia), Haemonchus L4 larvae and is basically ineffective against Oesophagostomum spp and Trichuris spp, other important gastrointestinal roundworms of sheep. It is also ineffective against lungworms (e.g. Dictyocaulus spp) and other roundworms that infect sheep outside the gastrointestinal system. Derquantel is also ineffective against tapeworms, flukes and any external parasites of livestock. Thus it can be considered as a narrow-spectrum wormer. This is probably the reason why it has not been developed as a stand-alone wormer, but only in combination with a broad-spectrum anthelmintic such as abamectin.

Abamectin, a veteran endectocide introduced in the 1980s, is considered as the "cheap" macrocyclic lactone. It is less potent and more toxic than ivermectin and other macrocyclic lactones but is often "good enough", although usually with a slightly narrower spectrum of efficacy and shorter protection periods than other macrocyclic lactones. Interestingly abamectin is widely used on livestock in Australia and New Zealand but so far not in the EU (excepting preciselyy this formulation), the USA and Canada. As for other macrocyclic lactones, abamectin has no efficacy whatsoever against tapeworms and flukes.

For resistance prevention, the use of mixtures of active ingredients with different mechanisms of actions makes a lot of sense when used against parasites that are susceptible (i.e. not yet resistant) to all the ingredients in the mixture. It is assumed that simultaneous development of worm resistance to both mechanisms of action is substantially more difficult and thus slower and less frequent than resistance to only one mechanism of action. In this case such mixtures may prevent or at least deleay appearance of resistance during years.

However, when such mixtures are used against parasites that are already resistant to one of the components in the mixture, the risk is significant that such parasites develop rather quickly resistance to the other component(s) as well, and thus become multi-resistant. Initially, such mixtures are indeed helpful. But in the long run they may worsen the resistance problem earlier than expected.

In ruminants, reducing the amount of feed slows down the exit flow of the rumen and prolongs the time during which the active ingredient remains there and is absorbed. Consequently it is advisable to reduce the access of animals to feed (especially to fresh pasture, not to water) 24 hours before administration. For the same reason, it is better to keep the animals away from food for about 6 hours after drenching. However sick or weak animals should not be kept away from food and fasting animals should have access to water.

Click here for general information on good practices for the prevention and control of gastrointestinal worms in livestock.


This article IS NOT A PRODUCT LABEL. It offers complementary information that may be useful to veterinary professionals and users that are not familiar with veterinary antiparasitics. 

Information offered in this article has been extracted from publications issued by manufacturers, government agencies (e.g. EMEA, FDA, USDA, etc.) or in the scientific literature. No guarantee is given on its accuracy, integrity, sufficiency, actuality and opportunity, and any liability is denied. Read the site's DISCLAIMER.

In case of doubt contact the manufacturer or a veterinary professional.