Prescribed 3 day z pak after Thanksgiving 2004 for strep throat and sinus infection. Had severe abdominal pain during course and a couple of days afterwards. Also had swollen glands a few days after taking. Ended up back at the doctor for severe vertigo and headaches two days before Christmas. After all of the pain I went through the z pak did not clear up my sinus infection and I was put on another antibiotic.