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)

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


  • Cats & kittens 12 weels equivalent to  2.6 lbs. 1.2 kg bw, 1 pipette with 0.5 mL (equivalent to ≤40.8 mg/kg fipronil + ≤49.2 mg/kg methoprene + ≤62.5 mg/kg etofenprox)

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


  • LD50 (acute oral) in rats: ~882 mg/kg (according to MSDS, estimate based on active ingredients)
  • LD50 (acute dermal) in rats: >4000 mg/kg (according to MSDS, estimate based on active ingredients)
  • Estimated Hazard class calculated according to the WHO: II Moderately hazardous (based on the LD50,learn more)

Suspected poisoning? Read the articles on fipronil safety, etofenprox safety and methoprene safety in this site.
WARNING !!!: Never use on cats pipettes approved only for dogs or vice-versa. Learn more about spot-ons and their safety.

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


Risk of resistance? YES, low to moderate for:

So far there are only very few confirmed reports on flea resistance to fipronil, 25 years after its introduction for flea control. But there are rumors that the number of product failures is increasing, mainly in the USA. Fleas have developed resistance to several other insecticides (e.g. carbamates, organophosphates and pyrethroids) and are certainly capable of becoming resistant to fipronil as well. Experience shows that prolonged and uninterrupted use of any insecticide on fleas (including fripronil) bears the risk of resistance development. Flea resistance to pyrethroids is widespread worldwide.

There are no reports on resistance of brown dog ticks to fipronil, but moderate resistance to pyrethroids has been reported in several countries (e.g. Brazil, Panama, Spain, USA).

So far there are no reports on resistance of fleas to methoprene.

Alternatives to prevent resistance through product rotation:

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

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

Resistance of fleas and brown dog ticks 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 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 product is marketed (maybe under another TM): USA
GENERIC BRANDS available? YES, perhaps not with the same composition

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


FRONTLINE TRITAK for cats is a once-a-month flea+tick spot-on combining fipronil (kills fleas and ticks) with methoprene (inhibits the development of fleas) and etofenprox (kills fleas and ticks and repels ticks). It is a follow-up product for FRONTLINE TOP SPOT, MERIAL's original fipronil-only spot-on formulation introduced in the 1990s.

Administered about every 4 weeks 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. It also kills several tick species (e.g. Dermacentor variabilis, Ixodes scapularisRhipicephalus sanguineusAmblyomma americanum, etc,) and chewing lice (Felicola subrostratus).

Fipronil is a broad-spectrum insecticide and acaricide belonging to the phenylpyrazoles introduced introduced in the late 1980s (by RHÔNE MÉRIEUX → MERIAL). It is massively used in pets and agriculture, and also moderately used against household pests and in some countries in livestock too. There are hundreds of generic brands with fipronil.

Methoprene (also called (S)-methoprene) is a veteran insect development inhibitor introduced in the 1970s (by ZOECON) used moderately in pets and agriculture. It has no effect whatsoever on ticks, only on fleas. The logic of combining both active ingredients is to ensure that if a few fleas survive the killing effect of fipronil (what usually happens) development of their offspring is inhibited, because the eggs of the surviving fleas won't developed.

Etofenprox is a veteran broad-spectrum insecticide and acaricide pyrethroid introduced in the 1980s (by MITSUI). It is abundantly used in agriculture and against household pests. It is effective against fleas, ticks and mosquitoes. However, resistance of fleas and mosquitoes to pyrethroids is not uncommon, in the USA and elsewhere. This means that protection against these parasites may be lower or shorter than expected.

This combination of more than one active ingredients of different chemical classes makes also sense regarding resistance prevention, because it means attacking fleas or ticks through two or more different mechanisms of action, which is vastly assumed to help preventing or at least delaying resistance development.

Nowadays, after fipronil lost patent protection there are dozens of flea spot-on for dogs and cats with generic fipronil, alone or in several mixtures with other active ingredients. But not all the brands are available in all countries.

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.

Rather surprising is the use in cats of a product containig 15% etofenprox, a synthetic pyrethroid. Etofenprox is less toxic to cats than other synthetic pyrethroids, but as other pyrethroids it is only very slowly eliminated in the cat's organism, which enhaces it's toxicity. And it is administered at a very high dose of up to 62.5 mg/kg. With so many alternative products available, I would rather use on cats one that has no pyrethroids, particularly considering the very modest contribution of etofenprox to the spectrum of activity of the product.

My personal opinion is that the fierce competition for market share in this largest and most profitable veterinary market has pushed some companies to take too many risks in order to launch products that are "new" or at least "different" to those of their competitors. In fact it has become very difficult to be "new", "different" or really "superior" in a market driven mainly by generic active ingredients during the last decade. Once one company has taken the risk, others will follow and launch their "me-too" brand, to be sure they don't miss an opportunity.

For an overview and a list of the most popular pet antiparasitics for flea, tick, lice and/or mite 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.