Zolendronate (also known as zolendronic acid or Aclasta) is the most potent medicine in the bisphosphonate class currently available. Bisphosphonates work by preventing resorption of bone by inhibiting the function of bone-dissolving cells called osteoclasts. Bisphosphonates are commonly used in the treatment of osteoporosis and Paget’s disease, and are also used for preventing some forms of cancer from spreading in bone. Zolendronate is given by an intravenous infusion (into a vein in the arm in a “drip”) over about 15 – 30 minutes and can be given every 12 – 24 months as needed for treatment of osteoporosis. Treatment of Paget’s disease involves even less frequent infusions. Zolendronate increases the bone density in patients with osteoporosis, to about the same extent as other medicines such as alendronate (Fosamax), and is effective at reducing fracture rates by 35 – 70%. It also reduces bone pain in Paget’s disease. Other than flu-like symptoms after the first infusion, side effects from Zolendronate treatment are uncommon, and are in general no different from placebo-treated patients in randomised trials. It should be remembered that major fractures can be very serious, so this should be balanced against the small risk of ill effects from treatments. Treatment is usually accompanied by some calcium tablets and/or vitamin D tablets given at the time of the infusion, to keep blood calcium levels normal.
Side effects with Zolendronate include:
- About 30% of individuals may experience a flu-like feeling after their first treatment, which usually last 24 – 72 hours, but which can occasionally go on for longer, sometimes with associated muscle or joint aching. This usually responds well to regular paracetamol or an anti-inflammatory such a Nurofen or diclofenac. The chance of this side-effect occurring after second or third Zolendronate infusions is much lower (about 1 – 3%).
- Individuals with important pre-existing kidney damage can sometimes experience deterioration in their kidney function after the administration of Zolendronate. It is normal practice not to use Zolendronate in people whose kidneys are not functioning well.
- Very rarely, drugs in the bisphosphonate class can cause eye inflammation, which responds to appropriate treatment.
Rare side effects with Zolendronate include:
- Osteonecrosis of the jaw (ulceration in tooth sockets or the gums, observed in a small number of cancer patients receiving high-dose treatment but not increased in those treated for osteoporosis or Paget’s disease).
- Upper leg fractures (atypical subtrochanteric fracture). Reported rarely throughout the world and not yet proven to be related to bisphosphonate therapy, but the possibility exists. If the association becomes proven, present calculations show that about 300 fractures are prevented for each such fracture occurring.