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


  • FIPRONIL: 64 mg/mL (=6.4%) on the total volumen administered; 9.8% in the single pipette.
  • AMITRAZ: 58 mg/ml (=5.8%) on the total volumen administered; 8.8% in the single pipette.
  • METHOPRENE: 76 mg/mL (=7.6%) on the total volumen administered; 22.1% in the single pipette.

CHEMICAL CLASS of the active ingredient(s):


PARASITES CONTROLLED* (spectrum of activity)

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


  • Dogs, small 2 to 10 kg 5 to 22 lbs. bw: 1 pipette with 1.07 mL (equivalent to 34.2 - 6.8 mg/kg fipronil + 31.0 - 6.2 mg/kg methoprene + 40.7 to 8.1 mg/kg amitraz)
  • Dogs, medium 10 to 20 kg23 to 44 lbs. bw: 1 pipette with 2.14 mL (equivalent to 13.7 - 6.8 mg/kg fipronil + 12.4 - 6.2 mg/kg methoprene + 16.3 to 8.1 mg/kg amitraz)
  • Dogs, large 20 to 40 kg 45 to 88 lbs. bw:  1 pipette with 4.28 mL (equivalent to 13.7 - 6.8 mg/kg fipronil + 12.4 - 6.2 mg/kg methoprene + 16.3 to 8.1 mg/kg amitraz)
  • Dogs, very large 40 to 60 kg 88 to 132 lbs. bw: 1 pipette with 6.42 mL (equivalent to 10.3 - 6.8 mg/kg fipronil + 9.3 - 6.2 mg/kg methoprene + 12.2 to 8.1 mg/kg amitraz)

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


  • LD50 (acute oral) in rats: 750 mg/kg (according to MSDS)
  • LD50 (acute dermal) in rats: 5000 mg/kg (according to MSDS)
  • 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, amitraz safety and methoprene safety in this site.
WARNING !!!: Never use on cats pipettes approved only for dogs. Amitraz is toxic to cats! Never use on small dogs pipettes approved for large dogs. 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:

  • fleas, mainly the cat flea, Ctenocephalides felis

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 US. 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.

So far there are no reports on resistance of brown dog ticks to fipronil or amitraz, nor 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**?

  • Fipronil: GENERIC (introduced in the 1990s)
  • Amitraz: GENERIC (introduced in the 1970s)
  • Metophrene: GENERIC (introduced in the 1970s)

*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): Many countries, including the US and the EU.
GENERIC BRANDS available? YES, for fipronil + methoprene, maybe not for the specific mixture fipronil + methoprene + amitraz.

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


CERTIFECT is the combination of fipronil (kills fleas and ticks) with methoprene (inhibits the development of fleas) and amitraz (kills and repels ticks). It is a follow-up product of 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 spp, Ixodes spp, Rhipicephalus sanguineusAmblyomma spp, Haemaphysalis spp, etc,) and chewing lice (Trichodectes canis).

Fipronil is a broad-spectrum insecticide and acaricide belonging to the phenylpyrazoles 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.

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 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.

Amitraz is an amidine acaricide and insecticide introduced in the 1970s (by BOOTS & CO). Amitraz was the first amidine (also called formamidines) used against ticks on cattle and it followed the organochlorines and organophosphates that had been discovered in the 1950s-1960s. It is still massively used in livestock in tropical and subtropical regions, but rather scarcely in pets. It is also used in agricultural pesticides. Amitraz kills and repells ticks but has no effect whatsoever on fleas. It is toxic both to cats and horses. 

This combination of more than one active ingredient of different chemical classes makes also sense regarding resistance prevention, because it means attacking fleas or ticks through two 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-ons for dogs and cats with generic fipronil, alone or in several mixtures with other active ingredients. But not all the generic 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.

This product is one of several examples of a questionable practice regarding the use amitraz for dogs at very high concentrations. Amitraz is an excellent tickicide, an has been used for years on dogs in impregnated collars and in other topical applications (soaps, baths, etc.). It is vastly used on cattle but not in ready-to-use pour-ons (comparable to the ready-to-use spot-ons for dogs), because cattle just don't tolerate it at high concentrations. Instead there are topical amitraz sprays or dips that are applied to cattle at concentrations of ~0.025% (250 ppm = mg/L), which results in a dose of 3-5 mg/kg body weight. Even at this dose cattle may not tolerate amitraz and show undesirable side-effects (sedation, depression, etc). Use of CERTIFECT results in a dose of up to 40.7 mg/kg amitraz for a 2 kg dog, a 10-fold dose than the one used on cattle. It is not surprising that not all dogs tolerate such a dose, particularly small breeds, puppies and weaker animals (sick, stressed, old). Chihuahuas, other small breeds and puppies are therefore particularly at risk of amitraz side effects. Needless to say that improperly administered to cats such a dose can be fatal.

A similar questionable practice regards the use of pyrethroids at very high concentrations on pets. In fact, serious problems with adverse reactions after use of certain spot-ons have been reported in the USA, especially on cats and small dogs. According to a report by the EPA from 2010, most problems occurred with spot-ons containing permethrin, phenothrincyphenothrin (all are synthetic pyrethroids) and amitraz, not approved for use on cats but erroneously used on them. There have been also numerous overdosing cases of small dogs, apparently because some users buy large vials for large dogs but use them several times in smaller dogs to save money. It seems also that small dogs are more sensitive than large ones and don't tolerate the treatment as well as large ones. It also seems that some insufficiently investigated inert ingredients (e.g. solvents) in the formulations are not as harmless as they were supposed to be.

My personal opinion is that the benefit achieved by adding amitraz to the formulation (faster tick detaching effect; a certain repellent effect on ticks; a few more tick species controlled) is not worth the significant risk of toxic side effects due to amitraz, particularly in small dogs or puppies.

It is also my personal opinion 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 "different" to those of their competitors. In fact it has become very difficult to be "new" 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. 

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