I started fever on Wednesday, on Thursday I saw my Dr., she prescribed Zpak. She did a chest X-ray and determined it is not pneumonia. On Thursday evening my fever spiked to 104.6, with Tylonol I could reduced it to 101.5. Friday morning (today) the fever broke. At 08:00 I was 99.0, then at 10:00 I was at 98.9 By 2:00pm I m back up to 101.5, even being my second day into the antibiotic. Why would a fever break, then return, especially when I m the second day into heavy antibiotic?