I have 3 dogs (2 shelties and 1 cocker spaniel) and buying heartworm and flea products can get quite expensive.

I buy Interceptor Spectrum for the shelties and a generic type of Heartgard for the cocker spaniel to prevent heartworm.

I use Frontline Plus for fleas and ticks-- I buy an extra-large and use a syringe to divide it among the three dogs. It was working great, but lately, I've been finding fleas on the shelties.

I found online that sometimes fleas can become resistant to the Frontline (they're still rendered sterile, so they won't reproduce). They recommended using Advantage or K9 Advantix occasionally to get rid of any resistant fleas. (I've also used Capstar to kill any that are on the dogs.)

My question is: Has anyone tried splitting a large vial of K9 Advantix among multiple dogs? It certainly does save a LOT of money. My sister said that her vet had told her that splitting the Frontline is fine, so hopefully it will work with Advantix as well.

Any advice or input will be appreciated! My dogs have been flea-free for 5 years on the Frontline Plus. I suspect that the squirrels are bringing in the fleas this year.