Brand: RAMETIN ® Sheep Drench


DELIVERY FORM: «drench» for oral administration.

ACTIVE INGREDIENT(S): naphthalofos  800g/kg (equivalent to 80%).

CHEMICAL CLASS of the active ingredient(s): organophosphate


PARASITES CONTROLLED (spectrum of activity)



  • Rametin is available as a 1.5 kg powder in a 10L container and mixes readily with all types of water. It's high suspensibility ensures a consistent and uniform suspension during drenching.
  • When mixed with water it resuts in a suspension drench containing 120 g naphthalofos/L
  • Rametin Sheep Drench is stable after mixing for up to 3 months
  • Dosage:
Bodyweight (kg) Dose mL (mg/kg)
6 - 7.5 2 (40.0 to 32.0 mg/kg)
7.6 - 9 2.5 (39.5 to 33.3 mg/kg)
9.1 - 12 3 (39.6 to 30.0 mg/kg)
12.1 - 16 4 (39.7 to 30.0 mg/kg)
16.1 - 20 5 (37.3 to 30.0 mg/kg)
20.1 - 28 6.5 (38.8 to 27.9 mg/kg)
28.1 - 40 9 (38.4 to 27.0 mg/kg)
40.1 - 52 13 (38.9 to 30.0 mg/kg)
52.1 - 68 17 (39.2 to 30.0 mg/kg)
68.1 - 90 22 (38.8 to 29.3 mg/kg)


  • LD50 (acute oral) in rats: Naphthalophos a.i. 88 mg/kg (according to MSDS)

Naphthalofos is significantly more toxic than most modern anthelmintics. It is used at a concentration that is only about twice the LD50 (for rats). This means that dosing mut be as accurate as possible, because twice the recommended dose may already cause toxic symptoms.

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

  • Meat: Australia: 7 days (ESI = 7 days)
  • Milk for human consumption: Australia: do not use in female sheep, which are producing or may in the future produce, milk or milk products for human consumption.

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

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


Risk of resistance? YES, resistance of gastrointestinal roundworms to most anthelmintic classes 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.

The increasing resistance problems of gastrointestinal roundworms to almost all modern anthelmintics (e.g. levamisole, benzimidazoles, macrocyclic lactones) has caused a partial return to old organophosphates (mainly naphthalophos and trichlorfon) in several countries (e.g. Australia, Argentina, Uruguay, etc). Organophosphate compounds are being increasingly used in rotation programs aiming at preventing or at least delaying the development of resistance. The reason is that their mechanism of action (they are so-called acetylcholinesterase inhibitors) is different from that of modern anthelmintics. So far there are rather few confirmed reports on resistance of gastrointestinal roundworms to organophosphates (e.g. in Argentina and Uruguay), but the risk of future development of such resistance is real in case of uninterrupted use of such products in the same property for years.

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

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**?


*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
GENERIC BRANDS available? YES, but not too many

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

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


RAMETIN SHEEP DRENCH is a local drench brand from BAYER (now ELANCO) containing 80% naphthalophos.

Naphtalofos is an old organophosphate introduced in the 1960s (by BAYER). Organophosphate anthelmintics (e.g. coumaphos, naphthalofos, trichlorfon) were abundantly used in livestock in the 1950s-1970s but starting in the 1960s they were quickly replaced by more effective and safer anthelmintics (e.g. levamisole, benzimidazoles, macrocyclic lactones) and were almost abandoned. As already mentioned, increasing resistance to modern anthelmintics has led to their re-introduction in some countries. Naphthalofos controls some gastrointestinal roundworm species in sheep, but only the adult worms, not immature stages or inhibited larvae. 

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.