Can I double 2 small does of Advantix on my dog?

My partner and I are struggling with money. Our large Shepard (she weighs 60 lbs) has fleas really bad and is biting herself to death!! I lost my job, so money, even for myself, is tight! I got two "pest prevention starter kits" for medium dogs (up to 20 lbs) for free from my pet supermarket. It is "K9 Advantix 2". She is sorta old with long legs and a long stout, so many parts of her body she cannot even reach. Can I use both packs on her? I know they say to "follow directions," but at this point I am feeling like anything is better than nothing. What should I do?Can I use both packs (that would equal 40 lbs and she weighs 60 lbs). Please help! My doggy appreciates it!!

I suggest you either contact the company directly, or your vet for the best answer.

Look at how much fluid liquid is in the single small Advantix pack and see if adding two equals the same amount of liquid as the large size Advantix