Brand: FELEX ® PLUS All Wormer Paste for CATS

Company: ZOETIS

FORMULATION: «paste» for oral administration, delivered in 2.64 ml pre-filled syringes


CHEMICAL CLASS of the active ingredient(s):


PARASITES CONTROLLED* (spectrum of activity):


  • Each 2.56 g syringe will treat up to 4 kg (equivalent to 57.6 mg/kg pyrantel embonate, 160 mg/kg niclosamide)
  • 1 kg mark in the syringe for every 1 kg bw

* Can be slightly different in some countries: read the product label!


  • LD50 (acute oral) in rats: n.a. for the tablets. >5000 mg/kg for pyrantel; >5000 mg/kg for niclosamide
  • Estimated Hazard Class according to the WHO: not applicable for veterinary medicines

Suspected poisoning? Read the article on pyrantel safety and/or niclosamide safety in this site.

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


Risk of resistance development? VERY LOW.

There are no reports on resistance of cat roundworms to pyrantel or of tapeworms to praziquantel.

Learn more about resistance and how it develops.


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

  • Pyrantel: GENERIC (introduced in the 1960s)
  • Niclosamide: GENERIC (introduced in the 1950s)

*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 product is marketed: AUSTRALIA
GENERIC BRANDS available? YES, in some countries.

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


FELEX ® PLUS All Wormer Paste for CATS from ZOETIS is a wormer effective against roundworms and tapeworms

Pyrantel is a narrow-spectrum anthelmintic belonging to the chemical class of the tetrahydropyrimidines that was introduced in the 1960s (by PFIZER → ZOETIS). It  is effective against roundworms and a few tapeworms (depending on the dose) in the gut, but not against those in other organs (e.g. the lungs, the skin, etc). It controls the most important dog worms such as the roundworms Toxocara canis and Toxascaris leonina, the hookworms Ancylostoma caninum and Uncinaria stenocephala. It is used a lot in pets and horses but rarely in livestock. There are dozens of products for pets with generic pyrantel.

Niclosamide is another veteran, narrow-spectrum salicylanilide anthelmintic introduced in the 1950s (by BAYER). It is effective against several tapeworm species (e.g. Taenia spp) and rumen flukes (Paramphistomum spp) of livestock, but not against roundworms or any external parasite. It is scarcely used in pets because praziquantel is mostly preferred. Usage in livestock is marginal.

Pyrantel and niclosamide have no residual effect, i.e. they act against the worms during a few hours after administration but are quickly metabolized and excreted. For this reason treatment must often be repeated for certain indications.

For an overview and a list of the most popular pet wormers click here.


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.