Whenever I have gotten a Z pack, often for a sinus infection myself, I have always had diarrhea and extreme cramps within two hours. It has also never worked for me or anyone in my family as well as things like Amoxicillin and Augmentin. Would Amoxicillin work for you? Even if your insurance doesn't cover it, it is really cheap. It has few side effects, except for maybe diarrhea at the end and yeast, which is common for most antibiotics anyway.

Nancy