Zoledronic acid

Zoledronic acid is a type of drug called a bisphosphonate. It’s used to treat osteoporosis.  This is a condition when the bones become thinner or weaker. Some illnesses, like myeloma or secondary cancer of the bone, can cause weakness in the bones.

Normally, two kinds of bone cell work together to keep bones healthy:

  • osteoclasts destroy old bone cells
  • osteoblasts build new bone.

Some cancers can cause osteoclasts to work too hard, destroying more bone cells than are created. This can weaken the bone, cause pain, or increase the amount of calcium in the blood. Zoledronic acid can slow the action of osteoclasts, allowing the bone to recover. It also helps to lower raised calcium levels in the blood.

Zoledronic acid is given as an IV drip every 3-4 weeks, or sometimes as a single dose. There are some side effects associated with zoledronic acid. Not everyone having the treatment will have all the side effects. You should discuss any changes with your doctor or nurse.

Zoledronic acid (Zometa®)

Zoledronic acid belongs to a group of drugs called bisphosphonates. Bisphosphonates are commonly used to treat bone thinning (osteoporosis).

In certain situations, bisphosphonates can help protect your bones against some of the effects of secondary bone cancer, such as pain and bone weakness. Secondary bone cancer occurs when the original (primary) cancer spreads to form a new cancer (secondary cancer or metastasis) in the bone.

Zoledronic acid is often given alongside other cancer treatments. As well as being used for some types of secondary bone cancer, it has been shown to be effective for people with myeloma (a cancer of the plasma cells, which are a type of blood cell). It is also used to lower a raised calcium level in the blood.


The effect of cancer on the bones

When bones are affected by secondary cancer, increased amounts of calcium (the substance that helps to build bones) may be released into the blood. A raised level of calcium in the blood is called hypercalcaemia. It can cause symptoms such as feeling or being sick (nausea or vomiting), tiredness, irritability and sometimes confusion. Zoledronic acid can help reduce high levels of calcium.

Secondary cancer in the bones may cause them to weaken, and in some situations they may break (fracture). Zoledronic acid can help strengthen the bone and reduces the risk of fractures.

Cancer can affect the bones in different ways, and zoledronic acid is only helpful for some cancers that affect the bones. Your doctor or specialist nurse can tell you if it would be helpful for you.


How zoledronic acid works

In normal bone, two types of cells called osteoclasts and osteoblasts work together to shape, rebuild and strengthen existing bone:

  • osteoclasts destroy old bone
  • osteoblasts build new bone.

Myeloma and some secondary bone cancers can produce chemicals that make the osteoclasts work harder. This means that more bone is destroyed than rebuilt, leading to weakening of the affected bone. This can cause pain and means that the bone can fracture or break more easily.

Zoledronic acid targets areas of bone where the osteoclast activity is high. It helps bring the balance of osteoclast and osteoblast activity back to normal by reducing the activity of the osteoclasts. This can reduce pain and help strengthen the bone. It also means that less calcium will be lost from the bones.


How zoledronic acid is given

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


How long zoledronic acid is given for

If you are having zoledronic acid to reduce pain or strengthen your bones, you may need to take it for as long as it seems to be working.

Zoledronic acid to lower calcium levels is usually given as a single dose.


Possible side effects of zoledronic acid

Some people have very few side effects while others may experience more. The side effects described here won't affect everyone having zoledronic acid.

We have outlined the most common side effects but haven't included those that are rare and therefore unlikely to affect you. If you notice any effects that aren't listed here, discuss them with your doctor or nurse.

Increased pain

Sometimes pain in the affected bone can become worse for a short time when you start taking zoledronic acid. If this happens, your doctor can prescribe painkillers for you until it wears off.

Flu-like symptoms

These include a high temperature, chills, and pain in your muscles or joints. Let your doctor know if these effects are troublesome. It may be helpful to take mild painkillers.


Less common side effects of zoledronic acid

Drop in calcium levels below normal

This is extremely rare and usually only temporary. It is unlikely to cause you any symptoms.

Effect on the kidneys

Zoledronic acid can sometimes affect how your kidneys work. This doesn't usually cause any symptoms, and the effects are generally mild. Your doctor will check how well your kidneys are working during your treatment by doing blood tests.

Red or sore eyes

Your doctor can prescribe eye drops to ease this.

Anaemia (low number of red blood cells)

Symptoms of anaemia include feeling very tired and breathless. Your doctor can check whether you're anaemic by doing a blood test.

Headaches

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

Feeling sick (nausea) and being sick (vomiting)

If this happens, your doctor can prescribe very effective anti-sickness (anti-emetic) drugs to prevent or greatly reduce the sickness.

Jaw problems (osteonecrosis)

A rare side effect of zoledronic acid is a condition called osteonecrosis of the jaw. This is when healthy bone tissue in the jaw becomes damaged and dies.

Gum disease, problems with your dentures and some dental treatments, such as having a tooth removed, can increase the risk of this. So before you start taking the drug you'll be advised to have a full dental check-up.

During treatment with bisphosphonates it's very important to look after your teeth by brushing them regularly and having routine dental check-ups. Always let your dentist know that you're taking bisphosphonates.

Some of the symptoms of osteonecrosis can include pain, swelling, redness of the gums, loose teeth or a feeling of numbness or heaviness in your jaw. Tell your cancer specialist and dentist straight away if you have any of these symptoms.


Additional information

You may be asked to take calcium and vitamin D supplements while having treatment with zoledronic acid. Your doctor will let you know if this is necessary.

Non-cancer admission

If you’re admitted to hospital for a reason not related to the cancer, it’s important to tell the doctors and nurses looking after you that you’re having treatment with bisphosphonates. You should tell them the name of your cancer specialist so that they can ask for advice.

Emergency contacts

It’s a good idea to know who you should contact if you have any problems or troublesome side effects when you’re at home.


Back to Bisphosphonates

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