Hello & welcome, I am Dr. B, a licensed veterinarian & I would like to help you with your wee one today.
How long has he been off food?
How old is he?
What tests did his vet do? Did they give anything else besides an antibiotic?
What do you mean he isn't responding? Is he weak, collapsed, or comatose?
Has he had any retching, gagging, lip licking, drooling, or vomiting?
Are his gums nice and pink (not white/pale)? Moist or sticky?
If you press on his belly, does he have any tensing, tenderness, discomfort, or pain?
Could he have eaten anything he should not have (ie bones, toys, plants, chemicals, human meds, etc)?