A new osteoporosis medication, abaloparatide, was recently added to the PBS, so it seems a good time to discuss anabolic osteoporosis treatments – what they are, how they differ from standard therapy, and who should be considered for them.
Anti-resorptive vs anabolic osteoporosis medications
Most standard osteoporosis medications (bisphosphonates such as alendronate or zoledronic acid, and denosumab/Prolia) work by inhibiting osteoclasts – the cells that break bone down. They do not act on the osteoblasts, the bone-building cells.
Anabolic osteoporosis medications are the ones that act on the osteoblasts, and there are now three available in Australia:
- Romosozumab – a monthly injection that can improve bone density by up to 10–15% when used as initial therapy.
- Teriparatide – a daily parathyroid hormone analogue injection, now off patent and considerably cheaper.
- Abaloparatide – another daily parathyroid hormone analogue injection, and the most recent addition to the PBS.
Why the order of treatment matters
Previously, anabolic treatments were only PBS-subsidised if someone had a fracture while already on another therapy. The problem is that anabolic medications given after denosumab or bisphosphonates have a significantly reduced benefit – improving bone density by only a few percent, and with teriparatide, bone density at the hip can actually decline.
For patients with previous vertebral fractures, transitioning off denosumab to start an anabolic agent is often too risky because of the rebound vertebral fractures that can occur when denosumab is ceased.
Who is now eligible for anabolic treatment first line?
Thankfully, the PBS criteria are now in line with the evidence and anabolic osteoporosis treatments can be used as first-line therapy in the right patients, which means far greater benefit.
Anyone who has had a hip or vertebral fracture, or two fractures in the last 24 months, together with a T-score below −2.5 at any site (including the wrist or Ward’s area), is eligible for anabolic treatment as first-line therapy. These remain specialist-only medications, so a referral to an endocrinologist is required.
How I approach osteoporosis medication planning
When I discuss osteoporosis medications with a patient, I talk about sequential therapies, treatment holidays, and – ideally – using anabolic agents as first-line treatment where they are indicated.
Osteoporotic fractures increase mortality risk, and the goal is to prevent the first fracture and definitely to prevent the second.
It is great to have more therapies available. Before commencing a treatment that is difficult to cease, such as denosumab, I would make sure a longer-term plan has been considered – including whether an anabolic agent is the more appropriate place to start.