I had a horrible first infusion. But I am going back next year. They will do it entirely different. (don't know why they didn't do that from the start!!!) But I read the research and a VERY SMALL amount have reaction (like 1%?) and a one-hundredth of that percent have problems at the second infusion. My take on it is that the medicine causes a reaction in the places in your body that need help. I had the WORST reaction in my cervical spine and it turned out my bones were "mush". So I think the medicine goes where it needs to and that you just don't know that you really needed it there. I'm having positive results, and I'm going to stick with it even with the hardships because I NEED to have stronger bones. I went into menopause early, and it really caused havoc with my bone density. I go to UCSD for infusions and they are caring about making my next infusion better so they will slow it down and give less medicine. They have found that the dose can be lowered without compromising the result. Yes, it was the singularly most awful experience I've had but I'm not giving up.