Advantage for Cats: Dosage, Safety & Side Effects

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owner applying “spot-on” flea treatment in a cat

Advantage is a brand name for a topical, “spot-on” flea treatment and flea prevention product containing the ingredient imidacloprid. It is currently only available on the market as the newer Advantage II which came out in 2011, and as the combination product Advantage Multi.

Advantage For Cats Overview

Medication Type:
Flea adulticide/larvicide antiparasitic
Topical liquid solution
Prescription Required?:
FDA Approved?:
This topical medication is approved by the EPA for cats.
Life Stage:
Cats 8 weeks of age and older
Brand Names:
Advantage for Cats, Defense Care for Cats
Common Names:
Available Dosages:
This product is largely not available in the U.S. as it has been replaced by Advantage II. It is made in two dosage sizes: cats 9lb and under, and cats over 9lb.

In this article, you’ll learn about Advantage products for cats, the different ingredients found in each, the ranges of pests they target, possible side effects to consider, and some frequently asked questions.

About Advantage for Cats

Advantage’s main ingredient is imidacloprid. Imidacloprid works to kill fleas by acting on nicotinic acetylcholine receptors of the central nervous system, essentially causing paralysis and death of the flea.

Advantage “spot-on” products are applied to the surface of a small target area or “spot” of the skin, usually in front of the shoulders at the back of the neck.

Advantage collects in the oils of the skin and hair, allowing for continual release, lending to its 30 day period of efficacy. Per the product label, a single application of Advantage can start killing cat fleas within 2 hours and can kill all adult fleas within 12 hours. It must continue to be applied once a month to prevent the chance of further infestations.

It is important to note that while these pesky pests are affected by Advantage by coming in contact with the skin, and don’t have to actually bite a kitty to die, Advantage products for cats do not provide true repellency that would prevent fleas or ticks from coming in contact with a pet.

Also Read: 8 Best Flea Treatment For Cats- Knock Out Fleas With These Safe Treatments

What Does Advantage Do for Cats?

Advantage products contain imidacloprid, which works relatively fast to kill adult fleas.

Advantage II, which has essentially replaced Advantage, additionally contains pyriproxyfen, an insect growth regulator that also targets flea eggs and flea larvae. By targeting multiple life stages, Advantage II is thus effective against the entire flea life cycle, which is more effective at stopping flea infestations more quickly.

How Does Advantage Work on Cats

Advantage Multi is a different combination product that contains imidacloprid plus moxidectin. The addition of moxidectin provides a spectrum of action against ear mites, mosquito-borne heartworms, and the intestinal parasites roundworms and hookworms. Advantage Multi does not contain pyriproxyfen, so it is not effective against flea eggs and larvae, only the adult fleas.

Side Effects of Advantage for Cats

cat sitting with a bell collar

Although Advantage II products for dogs and cats contain the same active ingredients, the manufacturer does not advise using a dog product on a cat

When used properly, side effects to Advantage products for cats are uncommon. Advantage II is labeled only for cats at least 8 weeks of age and Advantage Multi is only for cats at least 9 weeks of age. Topical products like Advantage should never be ingested.

According to the product label for Advantage II, the most common side effects, though generally uncommon, include skin irritation and scratching at the application site. Digestive upset signs like excessive drooling, vomiting, and diarrhea have also been reported.

Advantage Multi reports similar side effects with the addition of a small number of cats showing signs of behavioral change like agitation and excessive grooming, as well as lethargy.

Imidacloprid and pyriproxyfen as found in Advantage II are generally quite safe, even if a little is accidentally ingested.

However, the products are very bitter tasting. If a kitty were to lick recently applied Advantage II off either themselves or a housemate, the bitter taste alone can lead to excessive drooling, agitation, and sometimes even vomiting.

According to DVM360’s article “Toxicology Brief: The 10 most common toxicoses in cats” this effect is typically not a true toxicity, but a sometimes dramatic reaction to the bitter taste. Providing milk or liquid from a tuna can help resolve the signs in short order.

To avoid this from happening, it is important to apply any topical flea/tick product to the skin in front of the shoulder blades at the back of the neck, a location even the most flexible cat cannot reach to lick. In multiple cat households where lots of co-grooming occurs, separating housemate kitties for up to 24 hours after application to allow the product to fully dry may be advisable.

Although Advantage II products for dogs and cats contain the same active ingredients, the manufacturer does not advise using a dog product on a cat, even if they are similar in weight. Sometimes, there are differences in the inactive ingredients between dog and cat products that would make them inappropriate to consider interchangeable.

And lastly, topical products like Advantage have been known to cause skin and eye irritation in people. It is best to avoid contact with the solution during application and to wash your hands after.

Is Advantage Safe for Cats? Using Caution With Other Flea/Tick Products

While Advantage II for Cats has been established as a safe product, the active ingredients may be found in other products in combination with other ingredients that are not safe for cats. This is especially the case with dog products like K9 Advantix II, which has a similar name and similar-appearing packaging. K9 Advantix II contains permethrin, which is extremely toxic to cats.

Fortunately, these products are now required to include a warning against use in cats. But just to be safe, when selecting a flea/tick product for your kitty, always make sure the product includes a picture of a cat and indicates the product is specifically for cats.

It is also always advisable if you have a pup and kitty who like to hang out together or groom each other, to separate them for 24 hours after applying a topical product to your dog, especially if the product contains permethrin.

If you have any concerns for potential toxicity, even if you think your kitty might have just licked some Advantage off her fur and is having a bitter taste reaction, it is always best to contact your veterinarian, or the ASPCA Animal Poison Control Center for further advice.

And lastly, topical products like Advantage II have been known to cause skin and eye irritation in people. It is best to avoid contact with the solution during application and to wash your hands after. Make sure to keep out of reach of children.

Also Read: Flea And Tick Medication Poisoning In Cats

Advantage for Cats Dosage

Advantage products are typically applied as a monthly treatment every 30 days for the best protection.

Always follow all instructions on the packaging for any topical product you use for your kitty. Advantage vials have a cap that needs to first be removed.

How to Apply Advantage for Cats

applying “spot-on” flea treatment in a cat

If you have any questions about application or safety for Advantage products or any topical product, make sure to get in touch with your veterinarian.

The tip of the cap is then inserted onto the tip of the vial and twisted to break the seal. The entire contents of the vial can then be applied by parting the fur and applying to the skin along the back of the neck in front of the shoulders where a kitty cannot reach to lick it off of himself.

While Advantage products are considered to be waterproof, make sure not to bathe your kitty within at least 24 hours of application. Bathing shortly before application may also reduce its effectiveness.

If for some reason you are unsure if the product was administered correctly or whether all of it was applied, it is usually safest to not apply an additional dose.

If you have any questions about application or safety for Advantage products or any topical product, make sure to get in touch with your veterinarian.


Advantage products for cats including Advantage II and Advantage Multi can be effective at treating and eliminating certain parasitic pests for your kitty. They are also relatively safe when used properly.

Topical flea treatment products like Advantage can all have different combinations of ingredients targeting different parasites, which can sometimes be confusing. Make sure to clarify any questions you have about the best product for your kitty by having a chat with your vet.

Frequently Asked Questions

Is Advantage for Cats Effective?

The ingredients in Advantage II for cats appear to be effective against fleas and assisting in clearing out flea infestations.

However, the question of flea resistance to products like Advantage II and the idea that they don’t work comes up often. The 2017 article “Perception vs. Reality: Insecticide Resistance in Fleas” from DVM360 that refers to an article published in American Veterinarian that same year addresses this topic. 

An entomology (“bug science”) professor from the University of California heavily investigated this question and concluded that while resistance has been seen to some flea control or prevention products, true chemical resistance in fleas with fipronil, imidacloprid, and some other newer products on the market has not yet been demonstrated.

In many cases, when a pup or kitty parent is still seeing live fleas on their pet after a product has been applied, this issue can most often be traced back to incorrect use or application of the product, as well as poor expectations.

Following are some common errors or misperceptions.

  • Incorrect application.(i.e. applied to the fur not the skin, failing to apply the whole volume of product, failure to properly puncture or open a vial prior to application).
  • Failure to apply to all pets in the household. If one pet brings fleas indoors, they can jump onto all pets in the home. If all pets are not treated at the same time, flea infestations can persist.
  • Bathing. Baths are a common go-to, especially when live fleas are seen. However, while waterproof, Advantage products need 24 hours to spread throughout the oils on the skin. Bathing shortly before or after application removes oils from the skin as well as possibly the product itself.
  • Not Treating Long-Enough.  It can sometimes take as long as 3 months to clear out a flea infestation. So while most veterinarians advise year-round protection against fleas and ticks, a product like Advantage should be used every month for at least 3 months during an active infestation. Flea eggs not cleared from the home environment are likely to continue hatching every couple of weeks, meaning a kitty that received only one monthly dose of Advantage can get re-infested again a few weeks later if the dose is not repeated the next month.
  • Not Treating Year-Round. Fleas have been known to over-winter indoors. Treating pets for only certain months of the year can leave open gaps in prevention for infestations to occur.
  • Failing to Treat the Environment. Because one flea can lay up to 50 eggs in just one day, the amount of eggs in a home environment with fleas can be staggering. If the environment is not treated effectively, continually hatching fleas may continue to be found on a treated pet.
  • Perceiving Products as Repellents. Always remember that most topical products like Advantage do not have repellency action, meaning that fleas and ticks must come in contact with the skin to be killed. Heavily-infested outdoor areas as well as poorly-treated indoor infestations can be sources for large numbers of adult fleas to “suddenly” appear on a treated pet.

If You Still Think There’s a True Product Issue

If you feel you have applied a product properly and are addressing a flea infestation according to your vet’s instructions and still feel that a product is not working well, make sure to bring those concerns to your vet or contact the manufacturer of the product. 

How Does Advantage Work on Cats?

Advantage II’s main ingredient is imidacloprid, which affects the nervous system of a flea, quickly killing adult fleas. It is supported by pyriproxyfen, an insect growth regulator, which targets flea eggs and larvae, effectively interrupting the entire flea life cycle. 

These ingredients act only on the pests they target, making the products safe when used properly. Advantage products are used topically by applying the contents of the vial to a small area on the skin, usually in front of the shoulders at the back of the neck. 

Within about 24 hours, the ingredients are carried by oils in the skin to protect the entire body of a cat. The slow release of the ingredients in skin oil secretions also allows for the 30 days of efficacy against fleas. 

Will Advantage Hurt My Cat?

The short answer is, not if you use one of the cat-only products and apply it properly. While a hypersensitivity or allergic response to one of the ingredients is possible, this is very rare and most cats tolerate the feline Advantage products quite well.

Not all, but most cases of topical flea/tick product reactions or adverse effects in cats come from either an improper product being used, or the proper product not being applied correctly.

Topical products like Advantage II and Advantage Multi are not meant to be ingested, and should be applied in front of the shoulders on the back of the neck where a kitty is least able to reach to lick. Application elsewhere on the body can provide an opportunity for a fastidiously grooming kitty to lick off and ingest the product.

In multiple pet households where housemate cats or dogs may lick or groom each other, it may be advisable to keep them separate from each other for 24 hours after application of a topical product to allow the product to fully disperse and dry. This is especially true if a product containing permethrin is applied to a dog in a household also containing cats.

Although changes in product labeling requirements have made things better, there can sometimes be confusion among pet parents when choosing products to apply, especially in homes with both dogs and cats. 

The K9 Advantix II products and Advantage II have very similar-sounding names and similar-looking packaging, but they contain different ingredients. K9 Advantix II contains permethrin, which is very toxic to cats. 

Always make sure the product you purchase has a picture of a cat on it and says that it is specifically used for cats. Product packaging is now required to have this information to help avoid confusion. Products like K9 Advantix II are also required to have a warning label against use in cats. If you have both canines and furry felines and both types of products at home, always make sure to double check which box you get the medication out of before applying it.

Which is Better for Cats: Advantage or Frontline?

Both Advantage products and Frontline products have different combinations of ingredients, so they can have different applications. Instead of thinking about which product is “better,” consider which product is more appropriate to your kitty’s needs.

Advantage II kills adult fleas and also targets flea eggs and larvae. Advantage Multi targets only adult fleas, but the moxidectin component can also kill ear mites and provide prevention for mosquito-borne heartworms and the internal parasites roundworms and hookworms. 

The Frontline products Frontline Plus and Frontline GOLD contain fipronil, which kills fleas but also kills ticks, lice, chiggers, and even the sarcoptic mange mite. Both Frontline products also contain (S)-methoprene, which targets flea eggs and larvae. Like Advantage II, Frontline GOLD also contains pyriproxyfen, making its effect on killing fleas more efficient. 

In terms of the time it takes to kill fleas, Frontline GOLD starts killing fleas within 30 minutes, Advantage II within 2 hours, and Frontline Plus within 4 hours. Frontline Plus kills all fleas within 12-18 hours. Advantage II can kill all fleas within 12 hours and Frontline GOLD is likely comparable.

So all the products do very similar things as far as addressing fleas minus Advantage Multi which can only kill adult fleas. 

So when choosing between the products, consider the other things they bring to the table. If you live in a heavily tick-infested region and especially if you have a kitty that goes outdoors, a product with tick prevention would be higher on the list. 

Similarly, about the best thing we can do for heartworms in cats is to provide prevention, since there is no safe and effective treatment, so in heartworm endemic areas, a product like Advantage Multi that can prevent heartworm disease would be advantageous. 

One final note is that because Advantage Multi is a heartworm preventative, it is not available over the counter like all of the other products discussed in this article, and must be obtained through a prescription from your vet.

There is no topical product as of yet for kitties that does everything, so always carefully consider the benefits and detractors of each. Because there are so many products out there and they all seem to be slightly different from each other, it can get confusing. Make sure to give your vet a call to ask about what product he or she would recommend for your kitty.

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About Dr. Chris Vanderhoof, DVM, MPH

Dr. Chris Vanderhoof is a 2013 graduate of the Virginia-Maryland College of Veterinary Medicine (VMCVM) at Virginia Tech, where he also earned a Masters in Public Health. He completed a rotating internship with Red Bank Veterinary Hospital in New Jersey and now works as a general practitioner in the Washington D.C. area. Dr. Vanderhoof is also a copywriter specializing in the animal health field and founder of Paramount Animal Health Writing Solutions, which can be found at Dr. Vanderhoof lives in the Northern Virginia area with his family, including 3 cats.