Not all bisphophonates are the same – beware renal impairment

Clinical news
17 November 2018

A recent HDC case where a complaint was upheld against the GP highlighted the importance of checking a medications indications and contraindications.

View information about the case

In this case, a hospital pain clinic had recommended pamidronate infusion for treating back pain from spinal stenosis and ‘sciatica’. Although this was an off-label use recommended by the pain clinic, this is not where the trouble arose.

The GP offered zoledronic acid, another bisphophonate, believing they were inter-changeable. The patient had been experiencing deteriorating renal function over the previous year, such that zoledronic acid was contraindicated.

The patient was given a consent form to sign, however there was no pre-infusion checklist to go through. The patient had an acute on chronic kidney injury, and died.

As is often the case, it is the accumulation of smaller errors that lead to a very serious outcome.

GPs are increasingly offering IV treatments for osteoporosis, cellulitis and other conditions. We have a duty of care to make these treatments as safe as possible.

Some key learnings

  1. Not all medicines in the same therapeutic group are interchangeable. GPs must check a medicine before offering it.
  2. If you are prescribing or administering a medicine, you must be aware of the precautions and contraindications.
  3. The use of a checklist for procedures will reduce the risk of serious errors.
  4. Beware of off-label use of all medicines.
  5. Electronic glomerular filtration rate from the lab is not as accurate as a calculated GFR that takes BMI into account.

Useful information

  • If available, use tools within your Patient Management System (PMS) to calculate glomerular filtration rate (GFR) that takes BMI into account,. Alternatively, online tools such as Kidney Net’s eGFR calculator are available.
  • More information on the safe use of IV therapy can be found on the bpac website.
  • Specific information on zoledronic acid can be found on the bpac website.

This information is provided in a September 2011 bpac article titled ‘Community-based IV administration: primary care reducing hospital admissions’:

Since September 2010, the bisphosphonate zoledronic acid (Aclasta) has been funded under Special Authority for the treatment of oesteoporosis and Paget’s disease. The medicine may be prescribed and administered in a General Practice.

Zoledronic acid is given once a year, as a slow IV infusion delivered over a period greater than 15 minutes. Patients must sit, or stand, upright for 30 minutes after taking bisphosphonates orally, therefore zoledronic acid is a useful alternative for people unable, or unwillingly, to do this. IV infusion can be delivered by a trained Practice Nurse in any clinic with space available for 30 minutes. IV infusion can also be considered for people likely to be non-compliant with oral treatment or people who are intolerant to oral bisphosphonates due to gastrointestinal problems.

As there have been reports of renal impairment associated with zoledronic acid, it is important that it is not given to patients with a creatinine clearance below 35 mL/min. Patients should also be sufficiently hydrated before, and after the infusion, particularly if they are taking diuretics, or any other medicines that impact on renal function.17

Zoledronic acid is contraindicated in patients with hypocalcaemia and it is recommended that serum calcium levels be assessed if the patient has; vitamin D deficiency, recently undergone thyroid or parathyroid surgery or has calcium malabsorption.18 Patients with Paget’s disease of the bone need adequate calcium and vitamin D and may benefit from calcium supplementation for two weeks following infusion.

In the first few days following treatment, some patients may complain of flu-like symptoms. These symptoms usually resolve within a day or two and may be alleviated by taking paracetamol with 500 mL of water following the infusion. This has the added benefit of promoting hydration.

To read the full article and see reference material, please visit the bpac website.