>these drugs have side effects. what if you experience the side effect right after the dose is given?<
The major side effects of biphosphonates are gastrointestinal, hence the somewhat complicated dosing guidelines for oral medications (remain upright for half an hour, take with a full glass of water). It doesn't seem difficult, but on a population basis...well...
So it's unlikely that there will be many immediate side effects associated with administration of an IV bisphosphonate. Of *much* greater concern is the potential for osteonecrosis of the jaw (ONJ) occurring after dental surgery. If you've been to the dentist recently, you'll have noticed that they now have a check box asking whether the patient has taken a bisphosphonate. If a patient needs an extraction 6 months after taking Reclast, they're at higher risk for ONJ.
I think the risk for ONJ--low though it is--is one reason why Amgen's denosumab will be a success.