Years ago when I wasn't feeling well I took zpak. Back then, I had no idea how to take it so I just took it in the morning before I ate. Each time, I had this nauseated feeling, but I just ignored it because I thought it was just my sickness. By day 3 or 4, I vomitted for about 2 hours and then for the rest of the day had diarrhea. I just thought it was the zpak. Then, another time, I took another med when I was sick...took it in the morning before I ate, and the same thing happened. I finally concluded that it was because I had taken it without food.
So...after that, I always take those type of meds after I've eaten something. Since then (which was about 7-8 years ago), I have not had any sort of nausea from zpak or the other.
Conclusion: never take without eating first! Hope this helps!