Does Novamox Cause Fever And Throat Ulcer In Kids?

My 10 yr old grandson was prescribedNovamox 250 DT, 2 1/2 tabs in morning and 2 1/2 in night for ear infection. After 7 days, he started getting fever and ulcers in throat with vomitting feeling and inability to eat or drink anything. Dr asked him to continue Novamox for 3 days more but the boy could not. Can the ulcers be due to Novamox? Is the dosage prescribed high?