It is possible the flea medication had a severe negative effect on your dog as some spot-on flea medications can cause seizures and other serious side effects.
There have been some complaints of skin sensitivity to the medication, but I have not heard of the product causing disability. Have you taken the dog to a vet? Perhaps they can shed some light on what is causing the lack of movement. Good luck.
I applied Zodiac to my dog on Sunday morning. 24 hours later, he was exhibiting neurological issues and his walking was extremely wobbly. He is able to walk, but seems unsure of himself. He is in the hospital now.
