Frontline Plus Ingredients:
What are they and what do they do?

Many people often wonder what the Frontline Plus ingredients are and what they do exactly when it comes to killing fleas and ticks. You should be aware of the fact that Frontline Plus for dogs and cats contain the same ingredients.  However, the formula for cats and dogs varies in the amount of each ingredient used.

Although this has been covered in a couple of other places at Flea Bites 101, it is worth going over once again.  On the page comparing Frontline vs. Frontline Plus products for dogs, we explained how the new and improved Frontline Plus product was formulated differently and was more effective at killing fleas and preventing flea bites. You can read all of our reviews of various spot-on topical treatments for dogs.

Frontline Plus Ingredients

Frontline Plus contains two active ingredients whereas the original Frontline formula only had one.  Both products contain a chemical called Fipronil and it is used in dozens and dozens of different types of products all across the world.  In ultra simplistic terms this is the chemical that kills fleas and ticks and it does this by destroying an insect’s central nervous system and creating a state of hyperexcitation where muscles cannot relax.

However, it only kills adult fleas.

Around 2001, the manufacturer of Frontline  sought to introduce a more effective medication that not only killed adult fleas, but flea eggs and larvae.  This superior killing power attacked the entire flea life cycle and minimized the length of the infestation and the chances of re-infestation from occurring. The new product, Frontline Plus contains a second ingredient called (S)-methoprene.

(S)-methoprene is an insect growth regulator (IGR). Insect growth regulators like (S)-methoprene keep the levels of juvenile growth hormone in flea eggs and larvae artificially high.  Eggs and larvae hatch and grow through hormone signals.  When levels of juvenile growth hormones decrease to a certain level they undergo changes in their growth pattern and maturity.  (S)-methoprene keeps flea eggs and larvae juiced up on juvenile growth hormones and thus they fail to receive any signals to hatch or grow — essentially freezing the metamorphosis causing the eggs and larvae to die.

Formula Differences in Frontline Plus for Cats & Frontline Plus for Dogs

The active ingredients in Frontline Plus for Dogs is identical to the active ingredients listed in Frontline Plus for Cats.  We have no idea what, if any, differences there are in the inactive ingredients of each product.  On our pages where we reviewed the best flea treatment for dogs and the best flea treatment for cats, we discussed inactive ingredients as follows:

Active ingredients are the actual medicinal components that make you or your animal feel better. These are pharmacological components that actually have a therapeutic effect. The inactive ingredients are things that control the time-release duration of the drug, the size or shape of the pill, the consistency of the solution, taste and a wide range of other characteristics.

In most cases, as long as the active ingredients are the same patients will experience the same benefits of each drug (brand name vs. generic). However, some people may have different reactions to generics versus the name-brand product because of these inactive ingredient differences. In fact, some people may have allergic reactions to generic formulas and others just have bodies that respond differently.

Even though the list of active ingredients is identical, their respective formulas are slightly different.

Frontline Plus for dogs is 9.8% Fipronil and 8.8% (S)-methoprene.  Frontline Plus for cats is 9.8% Fipronil as well, but has a higher level of (S)-methoprene which clocks in at 11.8%.

VERY IMPORTANT: Please fully understand the following.  Each product has the same ingredients, but the ratio of each ingredient in the formula is different.  Also, the dosage amount differs in that dogs are given a larger dose of medicine.

Think of it in terms of ordering a pizza.

With Frontline Plus for dogs you would give your pooch a larger pepperoni and sausage pizza.  With Frontline Plus for cats you are going to give your kitty a small pepperoni and sausage pizza with extra sausage.