What Causes Discomfort In Elbow After Taking Zpack?

I started zpack on Friday. Since Saturday my left hand aches. Sometimes I get this jittery/buzzing brief feeling in my lower left arm around the elbow. I wonder (hope) this is a side effect of this med as I ve also experienced stomach aches off and on. I worry that I may be having a heart attack but feel silly . . .I m 49 and healthy otherwise. Just wondering if this med can cause extremity aching/pains.