Differences between Advantage Advantage II

Advantage I versus Advantage II

What is the difference between Advantage and Advantage II?

The main differences between Advantage and Advantage II for cats is that the original Advantage formula did not kill all stages of the flea life cycle. The new formula in Advantage II also kills the flea eggs and larvae. Advantage II contains imidacloprid and pyriproxyfen, which is an IGR or insect growth regulator. The pyriproxyfen is the chemical which prevents the growth of new flea eggs and larvae.

The original Advantage (Advantage 18 or sometimes called Advantage I) does not contain these ingredients and will not work as well to stop fleas on your cats. Additionally, fleas are evolving to be more resistant to flea medications which requires new formulas to effectively fight the fleas.

You want to make sure to get the newest formulas, or the old stuff may not even have any effect on your flea problem.

Larger cats require more strength to kill all of the fleas. Be sure to pick the Advantage II that corresponds to your cat’s weight.

Where to buy Advantage & Which one to get

If you have larger cats 9 pounds or over, then Bayer Advantage II Purple 6-Month Flea Control for Cats 9+ lbs. is the cheapest Advantage II price available anywhere and best bang for your buck. Its 6 doses and just as cheap as the 4 dose pack at Walmart! Don’t be fooled by those sellers on ebay with the Advantage kits. They are using Advantage for dogs which is a different formula and can result in serious adverse effects for your cat, possibly even death. There’s also the Bayer Advantage II Purple 4-Month supply for even cheaper.

If you have a smaller cat under 9lbs, then you’ll want Bayer Advantage II Orange 4-Month Flea Control for Cats 5-9 lbs.


Check out our new post explaining how you can save money on flea medication by buying larger packs of Advantage II and then measuring out smaller doses: Advantage II for Dogs on Cats – Is it safe?

Low priced Advantage II flea kits are available for purchase from FleaKitShop.com

We have ordered flea kits from this site for our cats and they worked great.

6 thoughts on “Differences between Advantage Advantage II

  1. Hi. I have found the following information:

    “Advantage II for large dogs is exactly the same product as Advantage II for cats.
    Dosing Advantage II for large dogs properly will give you the same effect as if you had purchased Advantage II for cats. The size of the dose is the only difference with this product.

    If you compare the ingredients on the labels, you will see that they are identical. NOTE: this is not so for Advantage Multi.

    • Actually, Advantage II for dogs is exactly the same as for cats. The ingredients are exactly the same, and the only difference is the amount of medication contained in each tube. This means that you can safely use Advantage for dogs and lessen the amount to proper dosage for your cat. Vets and animal shelters have been using this method to save money for many years. You just want to make sure to use a proper syringe applicator to measure exact dosages, as the dosage amount is extremely important and overdosing is very dangerous!

      I have personally been purchasing the large pack of Advantage II for dogs from here for a long time, and it always works great! Just be sure to get a small, 1ml syringe for measuring doses, and a small vial for storage of leftover medication. Its a great way to save money on your flea meds.

      Here’s the dosing measurements for using Advantage II for dogs (each tube from the extra large dog pack is 4ml)

      Cats under 5 pounds – 0.25ml
      Cats 5 – 9 pounds – 0.4ml
      Cats 10+ pounds – 0.8ml

  2. A local flea market seller has a bunch of backstock for Advantage 1… I bought some of it because it was really cheap, but it didn’t work on the fleas. I thought that Advantage was just no good but a friend linked me to this article on the changes with Advantage 2, so I tried it out and sure enough it killed the fleas! I have tried some of the other flea treatments also and so far the new Advantage 2 is working best.

  3. I was confused about the differences with advantage 2, but this info was exactly what I needed. Just ordered some for my kitties, thanks for the cheapest link!!

  4. I have safely used the large dog dose divided appropriately among several cats. For example, the dose of Advantage II for large dogs is 4.0 ml. The dose for small cats (under 9 pounds) is 0.4 ml and for larger cats is 0.8 ml. Therefore one large dog dose will cover 10 small cats or 5 large cats, or 4 large + 2 small.

    I spoke with a representative of Bayer and she verified that it is exactly the same formula, just more of it.

  5. The original Advantage is only something which hormonally disrupts the reproductive cycle of fleas. So of course it doesn’t “work” in that it doesn’t kill the fleas on the cat now, it works in the long term by reducing the general population of fleas. However Advantage II kills the adult fleas, which means the owner sees the effects immediately. Pick according to what you think is best.

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