Flea Medication for my 56 pound dog?

[Rosalie]

You might want to stick with Frontline - I'm not sure I would put Advantage on a Collie mix. The active ingredient in Frontline does not go into the dog's organs otehr than it's skin layer.

At that weight, you can still get away with the smaller dose, so long as there isn't a heavy infestation.
If there is, you can go for the larger dose, but err on the side of safety if your dog has never used it before, at least at first. No sense asking for more trouble.

Collies aren't the only breed to have the MDR-1 gene defect - it may be worth it to have her tested, just so you know - it can save your dog's life:
http://www.vetmed.wsu.edu/depts-vcpl/

[michelle]

Get the over 55 pounds one. You go by their weight, and if she is 56 pounds then you need to get her the over 55 pounds one.

[~Launi~AKINGisBorn~]

OVER. Always over. Over 55 lbs.

[cookie]

Use the K9Advantix, not the Advantage. The Advantix repels as well as kills and the repellent also repels mosquitoes.
I'd use the over 55 one to be sure.

If you have never used a topical before, watch your dog carefully as many of the Collies carry a gene referred to as the MDR1 gene making them highly susceptible to drug reactions. Not to worry you, just a warning and the fact that your dog is a mix might negate the gene anyhow.