What is zoledronic acid?

Zoledronic acid belongs to a group of drugs called bisphosphonates. It can be used to:

  • help protect the bones from the effects of some treatments for early breast cancer
  • reduce the risk of early breast cancer coming back – this is called adjuvant treatment
  • reduce a raised calcium level in the blood caused by cancer that has spread to the bones
  • treat bone weakness or pain caused by myeloma or by breast cancer that has spread to the bones.

Early breast cancer means the cancer has not spread beyond the breast or nearby lymph nodes.

Cancer that has spread to the bones is called secondary bone cancer. It happens when cells from the original (primary) cancer spread to form a new tumour (secondary cancer or metastasis) in the bone.

Myeloma is a cancer of a type of blood cell called plasma cells. The abnormal plasma cells build up inside bones causing pain and weakness.

The bones

Bones are living and constantly renew themselves. This helps bones keep their strength and shape.

Inside the bones, there are two types of bone cell:

  • osteoclasts, which break down and remove old bone
  • osteoblasts, which build new bone.

When we are children and young adults our bones keep getting thicker and stronger. But, as we get older, osteoclasts begin to remove more bone than osteoblasts make. This means our bones slowly become thinner (less dense). In some people, too much bone is lost and they have an increased risk of bone fractures.

Secondary cancer in the bones

Myeloma and some secondary bone cancers make chemicals that cause osteoclasts to work harder. This means that more bone is destroyed than rebuilt. The affected bone becomes weak and painful and can break more easily.

Bones contain calcium, which gives them strength. A bone affected by secondary cancer or myeloma may lose calcium into the blood. A raised level of calcium in the blood is called hypercalcaemia. This may cause you to have symptoms including:

  • feeling sick (nausea)
  • vomiting
  • tiredness
  • irritability
  • confusion.

How zoledronic acid works

Zoledronic acid reduces the activity of the osteoclasts. This can help reduce pain and strengthen the bone.

Zoledronic acid also reduces the amount of calcium that is lost from the bones. This helps calcium levels in the blood return to normal.

How zoledronic acid is given

Zoledronic acid is given by a drip (infusion) into the vein through a fine tube called a cannula. It is usually given in the outpatient department at the hospital. The infusion takes at least 15 minutes and is usually given once every 3 to 4 weeks.

How long zoledronic acid is given for

How long zoledronic acid is given for depends on why you are having the treatment.

  • If you are having zoledronic acid to help prevent the cancer coming back, you will have an infusion once every 6 months for 3 to 5 years.
  • If you are having zoledronic acid to reduce pain or strengthen your bones, your doctor will talk to you about how long you may need to take it for. You may need to have it for as long as it is working. It can take 2 to 3 months before you notice the full effects.
  • If you are having zoledronic acid to lower calcium levels in your blood, it is usually given as a single dose.

More information about this drug

We are not able to list every side effect for this treatment here, particularly the rarer ones. For more detailed information you can visit the electronic Medicines Compendium (eMC).

Possible side effects of zoledronic acid

Some people have very few side effects while others may have more. The side effects described below will not affect everyone taking zoledronic acid. If you are taking other drugs, you may have some side effects that we do not list here.

We explain the most common side effects here but have not included those that are rare and therefore unlikely to affect you. If you notice any effects that are not listed below, tell your doctor or nurse.

Increased pain

Sometimes pain in muscles or bones gets worse for a short time when you start taking zoledronic acid. If this happens, your doctor can prescribe painkillers for you until it gets better.

Flu-like symptoms

These include:

  • a high temperature
  • chills
  • pains in your muscles or joints.

Let your doctor know if these effects do not get better within a couple of days or are troublesome. It may be helpful to take mild painkillers such as paracetamol. Your doctor, nurse or pharmacist can give you advice.

Less common side effects of zoledronic acid

Allergic reaction

Rarely, this treatment may cause an allergic reaction.

Signs of an allergic reaction can include:

  • a faster heartbeat
  • swelling in your face
  • skin reactions
  • breathlessness
  • pain in your back, tummy or chest
  • a rash or bruising on your skin
  • flu-like symptoms.

Tell the nurse straight away if you think you may be having an allergic reaction. If you develop these symptoms when you are at home, contact the hospital straight away on the number you have been given. They can give you advice.

Numbness or tingling

You may notice numbness or tingling around the mouth or in the fingers and toes. This may be caused by low levels of calcium in your blood. You will have regular blood tests to check your calcium levels. Contact your doctor straight away if you have these symptoms.

You may be asked to take calcium and vitamin D supplements, unless you are having this treatment to lower the levels of calcium in your blood. Your doctor will let you know if any supplements are needed.

Effect on the kidneys

Zoledronic acid can affect how your kidneys work. Drinking plenty of fluids will help your kidneys work well. Your doctor will check how well your kidneys are working with regular blood tests.

Tell your doctor if:

  • you feel generally unwell
  • you have any swelling of your face, arms, legs or tummy
  • you notice a change in how often you pass urine (pee).

Red or sore eyes

Tell your doctor if you have red or sore eyes. They can prescribe eye drops to help.


Zoledronic acid may cause changes in the blood. For example, it can cause low level of red blood cells (anaemia). Symptoms of anaemia include feeling very tired and breathless. Your doctor can do blood tests to check this.


This is not common, but it is important to tell your doctor if you are getting headaches. They will advise you about what medicines to take. It is also important to drink plenty of fluids.

Feeling sick (nausea)

You may feel sick or be sick (vomit) during treatment for zoledronic acid. This is usually mild. Your doctor can prescribe anti-sickness drugs to help.

Take the drugs exactly as your nurse or pharmacist tells you to. It is easier to prevent sickness than treat it after it has started.

Pain in the thigh, hip or groin

Rarely, people on this treatment develop a break (fracture) in their thigh bone without any obvious cause. Sometimes both thigh bones are affected.

If you have any thigh, hip or groin pain, tell your doctor and mention that you are taking bisphosphonates. They can arrange tests to check the thigh bones for any signs of weakness or fracture.

Jaw problems

Rarely, this treatment can affect the jaw bone. Healthy bone in the jaw becomes damaged and dies. This is called osteonecrosis of the jaw (ONJ). It can cause:

  • pain
  • loosening of the teeth
  • problems with the way the gums heal.

The risk of jaw problems is higher after some types of dental treatment and in people who have gum disease or dentures that do not fit well.

It is important to avoid having any dental treatment that could affect your jaw bone when you are having bisphosphonates. This includes having a tooth or root removed or dental implants put in. It is fine to have fillings, gum treatments or a scale and polish.

To reduce your risk of developing jaw problems your doctor will advise you to:

  • have a full dental check-up before starting treatment
  • look after your teeth and gums during treatment (ask your dentist for advice)
  • tell your dentist you are taking a bisphosphonate before having any dental treatment.

Tell your cancer specialist and dentist straight away if you at any time you develop:

  • pain
  • swelling or redness in your gums
  • numbness or heaviness in your jaw
  • loose teeth.

Ear problems

Very rarely, bones in the outer ear may be affected by this treatment. Always tell your cancer doctor if you have any:

  • ear pain
  • discharge from your ear
  • ear infections.

You should also tell them know if you notice any other changes in your ears or hearing.

Other information

It's important to let your doctor know straight away if you feel unwell or have any severe side effects, even if they are not mentioned above.

Admission to hospital

If you are admitted to hospital for a reason not related to the cancer, it is important to tell the doctors and nurses that you are having treatment with bisphosphonates. You should tell them the name of your cancer specialist. This is so they can talk to them for advice.

Emergency contacts

It is a good idea to find out who you should contact if you have any problems or troublesome side effects when you are at home. The doctor or nurse at the hospital can advise you about this.

Other medicines

Some medicines can increase the side effects of this treatment or make it work less well. This includes medicines and supplements you can buy in a shop or chemist. Tell your doctor about any medicines you are taking, including over-the-counter drugs, complementary therapies and herbal drugs.

Pregnancy and breastfeeding

If you are pregnant, think you may be pregnant, or are planning to have a baby, ask your doctor or pharmacist for advice before taking this medicine.

Women are also advised not to breastfeed when taking this treatment. This is because the medicine may be passed to the baby through the breast milk.

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