- Prescribing Advice for GPs - https://www.prescriber.org.uk -

Annual infusion for osteoporosis

Zoledronic acid (Aclasta®) has been approved in Europe for the treatment of osteoporosis in post-menopausal women at increased risk of fracture. The summary of product characteristics has been updated to reflect this license extension.

The licence extension has been granted following publication earlier this year of the HORIZON-PFT study in the New England Journal of Medicine. This randomised controlled trial involved 7,765 women who were randomised to an annual infusion of zoledronic acid or placebo and followed up for 3 years.

The results of the study found a 70% relative risk reduction in vertebral fractures and a 41% relative risk reduction in hip fractures in the patients on active treatment. For hip fractures this is equivalent to a Number Needed to Treat (NNT) of 91 over 3 years to prevent one hip fracture. In monetary terms this means investing approximately £77,500 over 3 years to prevent one hip fracture.

There are data to show that compliance with bisphosphonate treatments is poor with some papers noting that half of patients stop taking treatment within the first year. This product may improve compliance by avoiding gastrointestinal side effects and simplifying the dosing regimen.

However, consideration needs to be given to the cost of treatment compared to existing strategies and also to delivery of the infusion. Based on the Drug Tariff price for alendronate 70mg, a year of treatment would cost £50.83 compared to £283.74 for zoledronic acid. A 15 minute infusion may also need to be undertaken in a secondary care setting which would invite an additional charge for service delivery.

Action: Clinicians should pro-actively check and encourage continued compliance in patients prescribed oral bisphosphonates. Zoledronic acid may be an option for patients who are unable to tolerate oral bisphosphonates due to intolerable side effects. Clinicians will need to investigate any local arrangements for administration of the infusion.