Zoledronate (zoledronic acid)

(Brand name: Aclasta®)

Zoledronate is a drug treatment for osteoporosis. You may hear zoledronate called zoledronic acid or by its brand name Aclasta. It can help to strengthen bones, making them less likely to break. It is given as an intravenous infusion (IV or 'drip') once a year. 

Zoledronate (zoledronic acid) is a type of medication called a bisphosphonate. Bisphosphonates are the most common treatments for osteoporosis. You may be offered zoledronate infusion if a drug treatment in tablet form isn't suitable for you, or if you have recently broken a hip. 

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What does zoledronate do and how does it work?

Zoledronate can help to make your bones stronger and reduce your risk of broken bones, including hip and spinal fractures.

Bones are made up of living tissue. The inside of our bones is constantly being broken down and rebuilt by specialist bone cells. As long as this process is in balance, your bones should stay healthy and strong.

But if the process becomes out of balance, our bodies can start to break down more bone than we build. This can cause the bones to become weaker and more likely to break easily.

Zoledronate works by slowing down the cells that break down bone. This helps to restore the balance and make your bones stronger.

You may still break a bone while taking zoledronate. If this happens, it doesn’t necessarily mean the drug isn’t working. No medication can stop all fractures, but taking zoledronate will make them much less likely.

Zoledronate is not a pain-relieving medicine, so it won't reduce any pain caused by broken bones. But there are other treatments and ways to manage pain

Who can have zoledronate?

Zoledronate may be suitable if you have osteoporosis, or if your risk of breaking a bone is high enough to need a drug treatment. It is often used in people who have recently broken their hip.

It is licensed for use in women who have been through the menopause, and for men. Doctors will occasionally offer zoledronate to younger women.

Most people are given tablets (daily, weekly or monthly) at first, rather than zoledronate. But your doctor may recommend zoledronate if tablets aren’t suitable for you.

You may also be offered zoledronate as a second drug treatment. For example, you might swap to zoledronate if you’re having problems with your first treatment. Or if you’ve been on your first drug for several years and your doctor has recommended a change.

Who should not take zoledronate?

Zoledronate may not be suitable if you:  

  • have a low blood calcium level (hypocalcaemia) – you’ll need to increase your intake of calcium and vitamin D before you can start zoledronate
  • have severe kidney problems
  • are pregnant or breast-feeding.


How is zoledronate given?

Zoledronate is given as an intravenous infusion (IV or ‘drip’) once a year. This will usually happen at a hospital, although some GP surgeries may occasionally give zoledronate. The drug is given via a needle into a vein. It takes at least 15 minutes to receive the full dose.

Before you start your treatment 

It’s very important to have enough calcium and vitamin D while you’re on zoledronate. Your doctor may advise you to take calcium and vitamin D supplements, to make sure you’re getting enough for your bones. 

Your doctor will recommend blood tests before each zoledronate infusion. This test is to check your calcium and vitamin D levels. If they are very low, your doctor may delay your treatment until your levels have improved. You may also have a blood test to make sure your kidneys are working well.

Make sure you drink at least one or two glasses of water, before and after each infusion, to avoid dehydration.


How will my treatment be monitored while I'm on zoledronate?

You’ll have an appointment once a year to receive your treatment. Contact your healthcare professional if you have any problems in-between these appointments. They may be able to suggest ways to help manage any side effects. 

If you break a bone while having zoledronate, speak to your GP. Breaking a bone doesn’t necessarily mean your treatment isn’t working. But it may be a good idea to have a bone health assessment.

After about three years on zoledronate, you should have a formal treatment review. At this review, your doctor will check if you still need a drug treatment, and that zoledronate is still the right drug for you.

You may have a bone density scan, which will give your doctor some information about your bone strength. But they will need to consider other things as well, such as whether you’ve broken any bones since starting on zoledronate.

There’s no clear way to prove for certain that your osteoporosis treatment is working. But research has shown that drug treatments like zoledronate are effective at reducing the risk of broken bones.

Following your review, your doctor may advise you to:

  • stay on zoledronate for another three years
  • stop treatment for a year or two, if this is safe for you – this is known as a treatment pause
  • start a different drug treatment instead of zoledronate
  • stop having any treatment.

Zoledronate is a long-lasting treatment and should keep helping your bones for about 2-3 years after you stop having it. Your doctor can advise you on what’s best for you, based on your own situation.


What are the possible side effects of zoledronate? 

As with any drug, zoledronate can sometimes cause side effects. The most common side effects are listed below as well as some rare problems. These rare problems might very occasionally happen after several years of treatment.

It is important to remember that in general, side effects are less common than many people think. Most people on zoledronate don’t have any problems. Even if you do get side effects at first, they usually improve quickly and there are ways to manage them.

For a full list of possible side effects, look at the patient information leaflet that comes with your treatment. If you don’t have a copy, ask your doctor or pharmacist for one.

It’s important to understand that many of these problems aren’t actually caused by the drug. When a medicine is first tested, the people taking it have to report anything unusual to the researchers. The problems they report are often just as common in people who aren’t taking the drug.

The following table has information on the main side effects and how common they are. For example, up to 3 in every 10 people who have zoledronate will get flu-like symptoms after their first dose. The other 7 in every 10 people who have the drug will not have this problem.

Side effect
How common is it?
What can I do about it?
Flu-like symptoms (such as fever, chills, muscle or joint pain, headache) 

Up to 3 in 10 after the first infusion

Much less common after later doses

These symptoms are very common after the first dose. They usually go away after a couple of days. A simple pain-relieving medication, such as ibuprofen or paracetamol, may help. Try not to plan anything very active for a few days, in case you get symptoms. You’re much less likely to get these symptoms after later doses.
Bone, joint or muscle pain

Less than 1 in 10

This usually improves as your body gets used to the drug. A simple pain-relieving medication, such as paracetamol, may help.
Fast and irregular heartbeat (atrial fibrillation)

Uncommon and not seen in all studies

This is unlikely to happen. But make sure your doctor knows if you have – or have an increased risk of – atrial fibrillation.
Eye inflammation, causing pain or blurred vision

Less than 1 in 100

Tell your doctor if you already have an inflammatory eye condition or develop symptoms such as a painful red eye.


Rare health risks:

Atypical (unusual) thigh bone fracture Less than 1 in 1,000 This is a rare type of thigh bone fracture that can occasionally happen after many years of treatment, even with little or no force.
Osteonecrosis of the jaw Less than 1 in 1,000 This is an extremely rare problem where healing inside the mouth is delayed, usually after major dental treatment. The general advice is to maintain good oral hygiene and have regular dental check-ups.

If you do get any side effects that don’t go away, it may help to:

  • make sure the problem isn’t caused by any other medication you are taking
  • tell your doctor or pharmacist, who may be able to help find out what is causing the problem
  • ask your doctor or pharmacist about other treatments that may suit you better.


Making a decision about zoledronate treatment 

As with any treatment, there are advantages and disadvantages to having zoledronate. You should think about these when deciding whether to have zoledronate, and about what’s important to you. Here are some of the main things to consider.


  • It can help to reduce your risk of broken bones.
  • It’s given as a drip once a year, so you can forget about it in-between doses.
  • It starts to work quickly and is effective for at least three years of use.
  • It keeps helping your bone strength for a while, even after you stop taking it.


  • You’ll usually need to visit your local hospital to have this treatment.
  • As with all medications, some people get side effects.
  • There are some possible health risks after several years of use, but these are rare.
  • Some people don’t like the idea of being on a drip.

If you've thought carefully about the advantages and disadvantages but still feel unsure, we have more information to help guide you through deciding whether or not to have a drug treatment


Content reviewed: March 2023

  • electronic medicines compendium (emc). Aclasta 5 mg solution for infusion - Summary of Product Characteristics (SmPC) [Internet]. 2020 [cited 2023 Feb 20]. Available from: https://www.medicines.org.uk/emc/product/210/smpc#gref
  • National Osteoporosis Guideline Group (NOGG). Clinical guideline for the prevention and treatment of osteoporosis. 2021.
  • Webster RK, Weinman J, Rubin GJ. People’s Understanding of Verbal Risk Descriptors in Patient Information Leaflets: A Cross-Sectional National Survey of 18- to 65-Year-Olds in England. Drug Saf. 2017;40:743–54.

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