Interceptor and Sentinel have primarily the same ingredients. Lately the vets have been recommending Sentinel plus which has an added ingredient to target another worm/parasite that has been showing up lately.
Anyway, all my dogs have been doing well on Sentinel/Interceptor, one of my dogs was a corgi (herding breed), however she was never tested for MDR1
Natural flea/tick remedies do not work, I would ask your vet what would be best for your dog.
I have had luck with Preventic collars they are supposed to be good for 3 months (I think 1 month is more like it) I get them at chewy dot com, they are reasonable there.
There is a new 8 month collar (flea/tick) that has been getting positive feedback, ask your vet about it.
K9 Advantix II topical is okay, except it gave one of my dogs a localized rash.
