I remember feeling like that after one dose of Lialda. I never took it again or any other drug that had the same ingrediant. It sounds like a allergic reaction. I would call your doctor immediately. I was about 2 minutes away from going to the hospital when everything subsided.
My daughter never has any trouble with Z-Pack. I, on the other hand, find the first dose (2 pills) especially rough - am sensitive even to ingredients in multivitamins.
BUT the doc told me to take a probiotic two hours after taking the Z-Pack (not sooner, or it would interfere with the med). So I took just one pill of Solgar's Advanced 40+ Acidophilus and it worked like a charm. THe probiotic has 1.5 billion microorganisms:
Lactobacillus Acidophilus - 300 million L. rhamnosus GG - 300 million
L paracasei - 300 million
B. lactis - 300 million
S thermophilus, 300 million