Arsenic trioxide (Trisenox, ATO)

Arsenic trioxide is a chemotherapy drug used to treat a type of acute myeloid leukaemia called acute promyelocytic leukaemia (APL). It is also called Trisenox or ATO. Arsenic trioxide is used as a first treatment for people with AML that has come back and also for people who have already had chemotherapy which included a retinoid called Tretinoin. There is also research looking into it as a treatment for other types of cancer.

Arsenic works by speeding up the death of leukaemic cells and encouraging normal blood cells to mature properly. It does this by working on particular proteins within the cell.

You have arsenic as a drip (infusion) into your bloodstream (intravenously). The drip lasts for between 1 and 2 hours. But if you have a reaction to the drip you may have it more slowly over 4 hours. You can have it through a thin, short tube (a cannula) put into a vein in your arm each time you have treatment. Or you may have it through a central line, a portacath or a PICC line. These are long, plastic tubes that give the drugs directly into a large vein in your chest. You have the tube put in just before your course of treatment starts and it stays in place as long as you need it.

You usually have chemotherapy as a course of several cycles of treatment. How many cycles of treatment you have depends on your treatment plan. There is detailed information about the way doctors plan chemotherapy in the planning chemotherapy section.

You may have arsenic trioxide to get rid of the leukaemic cells (induction treatment) or to stop your leukaemia coming back (consolidation treatment).

For induction treatment you have arsenic trioxide every day until there is no sign of the leukaemia in your bone marrow. This is called remission induction. You have this induction treatment for up to 60 days.

For consolidation treatment you usually have arsenic trioxide every day for 25 days. You have consolidation treatment 3 to 6 weeks after you finished induction treatment.

The side effects associated with arsenic trioxide are listed below. You can use the links to find out more about each effect. For general information, see our cancer drug side effects section.

More than 10 in every 100 people have one or more of the side effects listed below.

Temporary drop in the number of blood cells made by the bone marrow, causing

• Increased risk of getting an infection from a drop in white blood cells – it is harder to fight infections and you can become very ill. You may have headaches, aching muscles, a cough, sore throat, pain passing urine or feel cold and shivery
• Tiredness and breathlessness due to a drop in red blood cells (anaemia) – you may need a blood transfusion
• Bruising more easily due to a drop in platelets – you may have nosebleeds, bleeding gums after brushing your teeth, or lots of tiny red spots or bruises on your arms or legs (known as petechia)

Some of these side effects can be life threatening, particularly infections. You should contact your treatment centre if you have any of these effects. Your doctor will check your blood counts regularly to see how well your bone marrow is working.

Other common side effects include

• Fatigue in up to 6 out of 10 people (60%) during and after treatment – most people find their energy levels are back to normal within 6 months to a year
• Stomach pain in 6 out of 10 people (60%)
• Feeling or being sick – this is usually well controlled with anti sickness drugs
• Diarrhoea – drink plenty of fluid and tell your doctor or nurse if diarrhoea becomes severe, or continues for more than 3 days
• Numbness or tingling in fingers and toes, which can cause difficulty with fiddly things such as doing up buttons
• Muscle and bone pain
• Headaches
• Swelling of your legs, due to fluid build up known as peripheral oedema
• Fever and chills
• Inflammation of the membrane around the lungs – let your doctor or nurse know if you have pain in your chest when you breathe
• Retinoic acid syndrome in 1 out of 4 people – this causes shortness of breath, a high temperature (fever), chest pain, and fluid on the lung and heart. It most commonly happens 2 to 3 weeks after starting treatment and can become very serious. Tell your doctor or nurse immediately if you become breathless
• Raised blood sugar levels – you will have regular blood and urine tests to check this but let your doctor or nurse know if you feel thirsty or need to pass urine a lot
• This drug may have a harmful effect on a developing baby – do talk to your doctor or nurse about contraception before having treatment if there is any chance that you or your partner could become pregnant
• Loss of fertility – we don’t know exactly how this drug affects fertility so do talk with your doctor before starting treatment if having a baby is important to you

Between 1 and 10 in every 100 people have one or more of these.

• Heart problems – sometimes arsenic can affect the way your heart works, causing low blood pressure, dizziness, chest pain, or changes in heart rhythm (heart beat). These nearly always get better when treatment has stopped. You should tell your doctor if you have had heart problems before or if you have any of these side effects
• Loss of appetite
• Inflammation around the drip site – if you notice any signs of redness, swelling or leaking at your drip site, tell your chemotherapy nurse immediately
• Difficulty in sleeping
• Low mood and feeling anxious
• Confusion
• Feeling dizzy
• Skin changes – including a rash, dryness, itching or darkening of the skin
• Dry eyes and blurred vision
• Earache and ringing in your ears
• Cough and general shortness of breath
• Nosebleeds
• Fits (seizures)

There is a small risk that you may get a second cancer some years after arsenic trioxide treatment. There have been a few reports of people developing a second cancer after this treatment. It is not clear yet whether this was due to the arsenic or not.

You won’t get all these side effects. A side effect may get worse through your course of treatment. Or you may have more side effects as the course goes on. This depends on

• How many times you've had a drug before
• Your general health
• How much of the drug you have (the dose)
• Other drugs you are having

Talk to your doctor, pharmacist or nurse about all your side effects so they can help you manage them. Let your doctor know about any other medicines you are taking, including vitamins, herbal supplements and other over the counter remedies – some drugs can react together.

Arsenic trioxide is a relatively new drug in cancer treatment. This means that the information about side effects is based on only a few trials. And there is no information available at the moment about possible longer term effects that it may cause. Tell your doctor or nurse if you notice anything that is not normal for you.

You should not have immunisations with live vaccines while you are having this treatment or for at least 6 months afterwards. In the UK, live vaccines include rubella, mumps, measles (usually given together as MMR), BCG and yellow fever. You can have other vaccines, but they may not give you as much protection as usual until your immune system has fully recovered.

It is safe for you to be in contact with other people who've had live vaccines as injections. There can be problems with oral vaccines, but not many people in the UK have oral vaccines now. So there is usually no problem in being with any baby or child who has recently had any vaccination in the UK. You might need to make sure that you aren't in contact with anyone who has had oral polio, cholera or typhoid vaccination recently, particularly if you live abroad.