Antibiotics are always hard on a reptiles' internal metabolism. Particularly the gastrointestinal tract and the kidneys. Some (antibiotics) are more prone to affect these systems than others. Usually it's beneficial to make sure the reptile is on L.B.A. (lactobacillus acidophilus) while on antibiotics to replace the "good" bacteria of the g.i. tract that get killed off by the medicine. Dehydration is also a consideration thus the kidneys. Fluids also need to be given. Overall inappetance is a side effect of antibiotic treatment. All of these play into the reptiles' condition.