Brand: ACTIVYL ®


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

ACTIVE INGREDIENT(S)*: INDOXACARB: 195.3 mg/mL (= 19.53%)

CHEMICAL CLASS of the active ingredient(s): OXADIAZINE


PARASITES CONTROLLED* (spectrum of activity): Fleas

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


  • Dogs, small <6.5 kg <14 lbs. bw: 1 pipette with 0.51 mL (equivalent to >15.0 mg/kg indoxacarb)
  • Dogs, medium 6.6 to 10 kg14 to 22 lbs. bw: 1 pipette with 0.77 mL (equivalent to 22.8 - 15.0 mg/kg indoxacarb)
  • Dogs, large 10 to 20 kg 22 to 44 lbs. bw:  1 pipette with 1.54 mL (equivalent to 30.1 - 15.0 mg/kg indoxacarb)
  • Dogs, very large 20 to 40 kg 44 to 88 lbs. bw: 1 pipette with 3.08 mL (equivalent to 30.1 - 15.0 mg/kg indoxacarb)
  • Dogs, extremely large 40 to 60 kg 88 to 132 lbs. bw: 1 pipette with 4.62 mL (equivalent to 22.6 - 15.0 mg/kg indoxacarb)
  • Cats, small <4 kg ≈ <8.8 lbs. bw: 1 pipette with 0.51 mL (equivalent to >24.9 mg/kg indoxacarb)
  • Cats, large >4 kg  >8.8 lbs. bw: 1 pipette with 1.03 mL (equivalent to <50.3 mg/kg indoxacarb)

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


  • LD50 (acute oral) in rats: >2000 mg/kg (according to MSDS)
  • LD50 (acute dermal) in rats: >2000 mg/kg (according to MSDS)
  • Estimated Toxicity Class according to the WHO: III Slightly hazardous (based on the LD50, learn more)

Suspected poisoning? Read the article on indoxacarb 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.

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


Risk of resistance? YES, low in:

  • fleas, mainly the cat flea, Ctenocephalides felis

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

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 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**?

  • Indoxacarb: GENERIC (introduced in the 2000s)

*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.

ACTIVYL is MERCK AH's (formerly INTERVET) original once-a-month spot-on brand for dogs againts fleas based on indoxacarb, a pesticide licensed from DUPONT. Patent protection for indoxacarb has recently expired.

ACTIVIL TICK PLUS is a follow-up brand against fleas and ticks only for dogs.

COUNTRIES where this product is marketed (maybe under another TM): USA, EU, Australia, and other countries.
GENERIC BRANDS available? NO; so far no other brands with indoxacarb for use on dogs or cats have been introduced.

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


ACTIVYL was INTERVET's (nowadays MERCK AH) first once-a-month flea product for dogs and cats with indoxacarb only. 

Administered about every 4 weeks, ACTIVYL 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.

Indoxacarb is a broad-spectrum oxadiazine insecticide introduced in the 2000s (by DUPONT). It is used rather modestly in dogs and cats, not at all in livestock antiparasitics, and moderately in pesticides for agriculture and vector control. It is a so-called pro-drug: it becomes toxic only after it is absorbed and transformed inside the organism of selected insect species, mainly through esterase enzymes. The chemical class of the oxadiazines is relatively new, with a mechanism of action that is different from all other insecticides used against fleas.

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, 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.