FORMULATION: «spot-on» solution for topical administration on cats directly to the skin (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 ≤2.5 kg bw: 1 pipette with 0.3 mL (equivalent to ≥10.0 mg/kg fipronil & praziquantel ≥12.0 mg/kg methoprene, ≥0.5 mg/kg eprinomectin)
  • Cats 2.5 kg to 7.5 kg bw: 1 pipette with 1 mL (equivalent to 11.1-33.2 mg/kg fipronil & praziquantel, 13.3-40.0 mg/kg methoprene, 0.5-1.6 mg/kg eprinomectin)

* 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, eprinomectin safety, methoprene safety and praziquantel safety in this site.
WARNING !!!: Never use on dogs pipettes approved only for cats or vice versa. Never use on small cats pipettes approved for large cats. 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? Low for:

  • Fleas, mainly the cat flea, Ctenocephalides felis
  • Heartworm microfilariae

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 fipronil) bears the risk of resistance development.

There are reports on resistance of heartworm microfilariae to macrocyclic lactones in dogs in the Southern USA. This is a warning that sustained use of such chemicals against this parasite can lead to resistance.

So far there are no reports on flea resistance to methoprene, of cat tapeworms to praziquantel and of other roundworms to macrocyclic lactones.

Alternatives to prevent resistance through product rotation:

There are currently no alternatives to macrocyclic lactones for the monthly prevention of heartworm infections.

*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 to carbamates and organophosphates is not uncommon in several countries, including the US.

Learn more about resistance and how it develops.


Are the active ingredients ORIGINAL* or GENERICS**?

  • Eprinomectin: GENERIC (introduced in the 1990s by MERIAL)
  • Fipronil: GENERIC (introduced in the 1990s by RHÔNE-MERIEUX)
  • Methoprene: GENERIC (introduced in the 1970s by ZOECON)
  • Praziquantel: GENERIC (introduced in the 1970s by BAYER)

*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): The EU, New Zealand. Likely to become available in other countries.
GENERIC BRANDS available? No with such a particular composition, 

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


BROADLINE, introduced by MERIAL in 2014 is the combination of fipronil (kills fleas and ticks) with methoprene (inhibits the development of fleas), together with two anthelmintics, praziquantel that kills tapeworms, and eprinomectin that kills roundworms and prevents heartworm infections. It is one of the numerous follow-up products for FRONTLINE TOP SPOT, MERIAL's original fipronil spot-on formulation introduced in the 1990s.

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 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.

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 wont' developed. The combination of fipronil with methoprene, two active ingredients of different chemical classes, makes also sense regarding resistance prevention, because it means attacking fleas 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 cats with generic fipronil, alone or in several mixtures with other active ingredients. But not all the brands are available in all countries.

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. It also kills Ixodes ricinus ticks, but apparently not other tick species that can also infect cats.

Praziquantel is a veteran isoquinoline anthelmintic introduced in the 1970s (by BAYER). It is still the most effective and most vastly used parasiticide against tapeworms, but without any efficacy against roundworms, fleas or ticks. There are hundreds of antiparasitic brands for pets containing praziquantel, but rather few as a spot-on.

Eprinomectin is a macrocyclic lactone introduced in the 1990s (by MERIAL). It is effective against roundworms (including heartworm microfilariae), but not at all against tapeworms, fleas or ticks (at the recommended dose). For decades it has been used exclusively on cattle. BROADLINE is the first product developed by MERIAL with eprinomectin for use on pets. Eprinomectin has a similar spectrum of activity as ivermectin, which has been the macrocyclic lactone used by MERIAL in all heartworm preventatives (HEARTGARD) for dogs and cats during the last 25 years. Interestingly MERIAL has now preferred eprinomectin for BROADLINE, maybe because it is more appropriate for spot-on administration than ivermectin, which is administered orally.

The combination of all the four active ingredients in the same formulation results in a very large spectrum of activity, but it does not control "everything", e.g. it is not indicated for the control of mites or lice.

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 external 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 & heartworm 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.