Combination therapy refers to treating patients with more than one medicine. The medicines may be given at the same time or in sequence. The medicines in the combination are chosen because they work through different mechanisms. For a long time a common combination was hormone replacement therapy (HRT) and bisphosphonates, especially in postmenopausal women. HRT has fallen out of favor because of the side effects. Parathyroid hormone (PTH) analogs (Abaloparatide or Teriparatide) and bisphosphonates are a combination. Analysis has shown this type of combination is effective in increasing bone mineral density.
Doctors may choose a specific combination based on where fractures have occurred or where diagnostic techniques indicate low bone density, e.g. hip, spine, wrist, femur. Anabolic and antiresorptive agents at the same time or in sequence can yield good results.
Although not necessary, sometimes doctors feel osteoporosis patients would benefit from two drugs from different classes. And this isn’t just speculation by doctors. Scientific investigation has found that when patients get both anabolic and antiresorptive agents their bone density can go up faster than if they get just one agent. The sequence of the medicines can have an effect. If an antiresoptive agent is given after an anabolic one, it can consolidate the increase in bone density. One study found combining zoledronic acid treatment (one-time infusion) followed by daily teriparatide had benefits.
Further, anabolic therapy is usually limited to two years, so doctors typically keep patients on another medicine like a bisphosphonate after the end of the anabolic therapy. This is a sequential combination therapy but simultaneous combinations are also possible.
That doesn’t mean it’s easy or that any combination will work. But the idea has merit.
Hormone replacement therapy (HRT) was once widely used for postmenopausal women, and studies found it worked better when a bisphosphonate drug was added. At least, the combination increased bone density if the effects on fracture rates was less apparent. When paratharoid hormone and its synthetic analogs (e.g teriparatide) were first applied for osteoporosis, scientists looked into mixing PTH with HRT, and again, found increases in bone density with no reported effect on fracture rate.
A combination of PTH and bisphosphonates has proven better than PTH alone when it comes to increasing density in vertebrae and pelvic bones in one year of treatment, but PTH alone produced better density gains over a two-year period.