Company: VIRBAC

FORMULATION: «spot-on» solution for topical administration on the back of the animals (also called pipettes, squeeze-ons, drop-ons, etc.)


CHEMICAL CLASS of the active ingredient(s):


PARASITES CONTROLLED* (spectrum of activity)


  • Treatment and prevention of flea infestation (Ctenocephalides felis)
  • Treatment of ear mite infestation (Otodectes cynotis)
  • Treatment of notoedric mange (Notoedres cati)
  • Prevention of heartworm disease (L3 and L4 larvae of Dirofilaria immitis)
  • Treatment of infections with gastrointestinal nematodes (L4 larvae, immature adults and adults of Toxocara cati and Ancylostoma tubaeforme)
  • The product can be used as part of a treatment strategy for flea allergy dermatitis (FAD).


  • Treatment and prevention of flea infestation (Ctenocephalides felis),
  • Prevention of heartworm disease (L3 and L4 larvae of Dirofilaria immitis).

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


  • Cats small < 4 kg bw: 1 pipette with 0.4 mL (equivalent >10.0 mg/kg imidacloprid, >1.0 mg/kg moxidectin)
  • Cats, medium >4 to 8 kg bw: 1 pipette with 0.8 mL (equivalent 20.0 to 10.0 mg/kg imidacloprid, 2.0 to 1.0 mg/kg moxidectin)
  • Cats, large >8 kg bw: appropriate combination of pipettes

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


  • LD50 (acute oral) in rats: ~4500 mg/kg (estimate based on the LD50 of the active ingredients)
  • Estimated Toxicity Class according to the WHOIII moderately hazardous (based on the imidacloprid LD50, learn more)

Suspected poisoning? Read the article on imidacloprid safety and/or on moxidectin safety in this site.

WARNING !!!: Never use on cats pipettes approved only for dogs. Never use on small dogs pipettes approved for large dogs. Learn more about spot-ons and their safety.

Most heartworm preventatives contain macrocyclic lactones at a dose that kills microfilariae and ensures adequate protection for about 1 month, i.e. treatment has to be repeated monthly. In endemic regions with mild to warm climate it is recommended to treat the pets during the whole year, because mosquitoes can be infective the whole year through.

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


Risk of resistance? YES, mainly in:

  • fleas, mainly the cat flea, Ctenocephalides felis

So far there are no reports on flea resistance to imidacloprid, more than 20 years after its introduction for flea control. However, fleas have developed resistance to several other insecticides (e.g. carbamates, organophosphates and pyrethroids) and are certainly capable of becoming resistant to imidacloprid as well. Experience shows that prolonged and uninterrupted use of any insecticide on fleas (including imidacloprid) bears the risk of resistance development.

There are reports of resistance or tolerance of heartworm microfilariae (Dirofilaria spp) to ivermectin and other macrocyclic lactones in the USA (mainly in the South), probably including moxidectin as well. This has happened after about 20 years of very intensive use of such compounds there. This may happen elsewhere as well. Currently there are no other once-a-month treatments for heartworm prevention other than those containing macrocyclic lactones.

So far there are no significant resistance problems in mites, lice, heartworms and roundworms to moxidectin in dogs or cats.

Alternatives to prevent flea resistance through product rotation:

*F = effective against fleas; T = effective against ticks.

These alternative products may not be available in all countries, or may not be available as spot-ons.

Resistance of fleas to carbamates, organophosphates and pyrethroids is not uncommon in several countries, including the USA.

Learn more about resistance and how it develops.


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

  • Imidacloprid: GENERIC (introduced in the 1990s)
  • Moxidectin: GENERIC (introduced in the 1990s)

*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 (maybe under another TM): UK and other EU countries
GENERIC BRANDS available? YES; this produc is a generic version of BAYER'S ADVOCATE.

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


PRINOVOX is a once-a-month flea+heartworm spot-on from VIRBAC, a generic version of BAYER'S ADVOCATE = ADVANTAGE MULTI .

Administered about every 4 weeks it controls established flea infestations and prevents flea populations to develop in the pets environment, but only if all the dogs and cats in the same household are treated against fleas. Imidacloprid in this formulation has no effect whatsoever on mites, heartworms and roundworms. Moxidectin is not effective against fleas.

Imidacloprid is a broad-spectrum neonicotinoid insecticide introduced in the 1990s (by BAYER). It is abundantly used in pets, but very scarcely in livestock. It is massively used in agriculture and also quite abundantly against household pests.

Moxidectin is a systemic macrocyclic lactone introduced in the 1990s (by AMERICA CYANAMID → FORT DODGE → PFIZER → ZOETIS) effective against mites, heartworms and roundworms. It has no effect on fleas. It is moderately used in both pets and livestock. It is not used in agriculture or hygiene pesticides. The logic of the mixture with imidacloprid is combining once-a-month flea prevention with once-a-month heartworm prevention in the same product, plus the added benefit of mite and roundworm control.

The logic of the mixture with imidacloprid is combining once-a-month flea prevention with once-a-month heartworm prevention in the same product, plus the added benefit of licemite and roundworm control.

Topical products (mainly spot-ons and insecticide-impregnated collars) have some advantages over systemic products (mainly tablets for oral administration and injectables):

  • Most topical products kill or sterilize the parasites before they bite and suck blood on the pet, whereas systemic products kill or sterilize the parasites only after their blood meal.
  • Topical products cannot be vomited.
  • Spot-ons and collars are very convenient to administer.
  • There is a larger choice of topical products.

But topical products have also some disadvantages:

  • Topical products contaminate the pet's hair coat and it is advisable for children and also adults to avoid contact with the pet for several days after treatment.
  • Topical products may not control parasites in some parts of the pet's body (e.g. the ears, below the tail, between the legs, etc.), whereas systemic products reach the blood-sucking parasites through the blood wherever they are.
  • Efficacy of topical products may be reduced or shortened through exposure to dirt, sun, shampooing, washing, rain, baths, etc., whereas efficacy of systemic products is independent from these factors.

For an overview and a list of the most popular pet antiparasitics for flea & worm control control 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.