My Daughter nearly aged 3 has a chest infection. She has High temperatures for 5 nights now as high as 40.2.  Doctor has changed her anti biotic from Distaclor to Klacid.  At night time temperatures are the worse and during the day there low grade but she gets very tired on running around.  She has a corrected Congenital heart disease TGA which was repaired at birth.  Not sure if she needs IV Antibiotics - she is only on the klacid since today.
Welcome at Chat Doctor I have gone through your query and being your physician I completely understand your health concerns.  For how many days she is having fever? Is there any sputum in cough? What is the color of sputum? Have u done her chest X-ray?  As far as antibiotics are concerned, it takes at least 48 to 72 hrs to start its affect. You need to be patient with it and do complete the course in proper dose as prescribed by your doctor.  Klaricid is very good antibiotic for respiratory tract infection. You should use spy broken with it to relieve fever. Meanwhile stay calm and continue with the medicines may she gets well soon Hope your query is adequately ad Chat Doctor.