Wet cough and sudden loss of hind legs

My Sebastian developed a cough took him to the vet and he gave him a shot of antibiotics. Later that night Sebastian Baca me wobbly in his hind legs. Two days later now he has lost use of his legs. He still goes pee and tries to poop but it seems to be painful for him. He is approx 11 yrs old. Orange Tabby.

Was the injectable antibiotic Convenia? That is something that should never be used in cats because of the many adverse reactions to it. There are several threads about the risks of using Convenia here on TCS and a more in depth article by a vet at http://catinfo.org/?link=convenia

Coughing could be asthma or just allergies. Antibiotics won't help in either case. I'm not sure why some vets do a " one size fits all" treatment of antibiotics when the presented symptoms are not really indicators of a bacterial infection

Anyways, your cat needs to be seen by a vet for the loss of use of the hind legs. Seek out another vet if you don't feel that the current vet is providing the best treatment for your cat.