The number of osteoporosis drugs and the different ways they are taken can be confusing. There are pills, injections and infusions, taken weekly, monthly or at other intervals. Your doctor chooses the best drug based on a variety of factors. A small percentage of people who take bisphosphonates have gastrointestinal problems, such as nausea, stomach pain, constipation, diarrhea and gas. This may be one reason your doctor prescribed Prolia, which is given as an injection and is easier on the stomach.