HI, thanks for using healthcare magic Atrial fibrillation is one of the more arrhythmias (abnormal heart rates or rhythms). There are different potential causes though in some person no particular cause is found. There are number of different medications that can potentially cause atrial fibrillation but most antibiotics are not known to do this. It has been reported that azithromycin can cause abnormal heart rhythms in some persons but this is usually in persons with a previous risk of arrhythmias. In terms of the prednisolone, it is also not associated with this side effect though high doses of another steroid , methyprednisolone that can cause this problem. I hope this helps