My Son Is 2years An 9months.he Is Suffering From Severe

My son is 2years an 9months.he is suffering from severe cough and fever.doctor had prescribed Meftal along with Swich Dry syrup.but its not working.since 3days i am giving this dose in the day time he is feeling well,but in the night he is shiveringand trembling and there is severe cough and fever.kindly to advice pls.