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Arsenic Trioxide

Arsenic Trioxide is used to treat a type of blood cancer called acute promyelocytic leukaemia (APL). It may be used in combination with another medicine called tretinoin for patients with APL, or for patients whose APL has come back or has not responded to previous treatment with chemotherapy. The exact way Arsenic Trioxide works is not completely understood. It is thought to work by causing cancer cells to break down and die. It also damages a specific abnormal protein found in APL cancer cells, helping to stop the cancer from growing.

Article last reviewed 08 September 2026
17 mins read

What is this medication for?

Arsenic Trioxide is used to treat a type of blood cancer called acute promyelocytic leukaemia (APL). It may be used in combination with another medicine called tretinoin for patients with APL, or for patients whose APL has come back or has not responded to previous treatment with chemotherapy.
The exact way Arsenic Trioxide works is not completely understood. It is thought to work by causing cancer cells to break down and die. It also damages a specific abnormal protein found in APL cancer cells, helping to stop the cancer from growing.

How should I take or use this medication?

Arsenic Trioxide is given as an injection into the vein (intravenous infusion) over 2 hours. The infusion may be extended up to 4 hours if you experience certain reactions during the infusion.

What precautions should I take when taking or using this medication?

Inform your healthcare professional if:

You are allergic to arsenic or any of the other ingredients of this medication.
You are taking any other medications, including supplements, traditional medications and herbal remedies.
You have any other medical conditions, especially heart problems or kidney or liver problems.
You are going to receive any vaccination or surgery, including dental surgery.
You have any plans to start a family in the future.
- Arsenic Trioxide may affect fertility. Discuss fertility preservation options with your doctor before starting treatment.
Arsenic Trioxide is found in breast milk. As it may cause serious harm to a breastfed child, you should not breastfeed during treatment and for 2 weeks after the final dose.
Arsenic Trioxide can cause harm to an unborn baby. You should not become pregnant during treatment. You should use an effective birth control method during treatment.
- A pregnancy test should be done before starting treatment if you are a female of childbearing age.
- Females should use effective contraception during treatment and for 6 months after the final dose.
- Males with female partners who could become pregnant should use effective contraception during treatment and for 3 months after the final dose.

If you have any questions about this medication, please discuss with your healthcare professional.

What are some common side effects of this medication?

The table below lists some of the common side effects as well as the rare but serious side effects.

Side Effect	Management
Symptoms of drug allergy including one or more of the following: swollen face/eyes/lips/tongue, difficulty in breathing, itchy skin rashes over your whole body	If you experience any of these symptoms, you should seek medical attention immediately.
Differentiation syndrome — It occurs when the cancer cells mature too fast, releasing massive amounts of signals that cause severe inflammation and fluid leaks into the body's tissues. This can be life-threatening. Signs and symptoms may include unexplained fever, difficulty breathing, weight gain, fluid around the lungs or heart, low blood pressure, or kidney problems.	If differentiation syndrome is suspected, high-dose steroids and close monitoring will be started immediately. Arsenic Trioxide will be temporarily stopped. Proceed to the A&E department immediately if you experience these symptoms after you have left the hospital.
Slow or abnormal heart rhythm — irregular or fast heartbeat.	Your heart will be monitored with regular ECG tests weekly, and more frequently if needed. Proceed to the A&E department immediately if you feel faint, lightheaded, dizzy, or have a fast or irregular heartbeat.
Electrolytes abnormalities (e.g. low potassium, low magnesium, low calcium levels)	Your doctor will monitor your blood tests regularly during treatment and may prescribe supplements if required. If electrolytes abnormalities become severe, you may experience symptoms such as: Muscle cramps Numbness and tingling of hands and feet Abnormal heart rhythms Sleepy, drowsy or confused Seizures (in rare cases) Inform your doctor if you get the symptoms above.
Liver problems Rarely, this medication can injure or damage the liver. A liver injury may recover on its own. However, in some cases, it can cause serious liver damage.	Stop this medication and proceed to the A&E department immediately if you experience any of the following: Dark coloured urine Light-coloured stools Yellowing of your skin or eyes Nausea, vomiting that does not go away Severe abdominal pain
Problems with brain function (encephalopathy), which may include symptoms such as: Headaches Vision changes Feeling confused Seizures This is a rare but severe side effect.	Proceed to the A&E department immediately if you experience such symptoms.
Decrease in white blood cell count This may increase your chances of getting an infection.	To reduce the risk of infections: Maintain good hand hygiene. Wash your hands before handling food and after using the toilet. Avoid crowds and do not go near people who are sick. Wear a mask if necessary. Eat freshly cooked and well-cooked food. Avoid raw meats, vegetables and eggs, or half-cooked or uncooked food. Proceed to the A&E department immediately if you have any signs of infection, such as having A fever of 38°C and above Chills Bad sore throat Pain when you pass urine Mouth sores or wounds that do not heal You should avoid taking Paracetamol to relieve fever as this may mask your fever and delay the treatment of your infection.
Decrease in platelet count Low platelet levels can increase your chance of bleeding.	To reduce the risk of bleeding: Be careful when using sharp objects such as scissors or knives. Brush your teeth gently with a soft bristle toothbrush to prevent gum bleeding. Try not to bruise, cut, or knock yourself. Apply direct pressure to any cuts or wounds to help stop bleeding. Proceed to the A&E department immediately if you have symptoms of serious bleeding including: Blood in the urine Black, sticky or bloody stools Unexplained large bruises Coughing up blood or coffee ground-like vomit Bleeding that does not stop
Nausea or vomiting	Take small and frequent meals. Avoid foods or smells that may make you feel nauseous, such as oily, fried, or strong-smelling food. Avoid tight-fitting clothes around the waist. Your doctor may prescribe medications to help relieve or prevent nausea or vomiting. Take these as instructed.
Skin rash	Avoid hot showers. Use cool or lukewarm water to bathe. Apply a moisturiser to areas with dry skin. Avoid staying out under the sun. Use sunscreen with Sun Protection Factor (SPF) of at least 30 and covered clothing when you are out in the sun. Please see a doctor immediately if the rashes are painful, blistering, or affect a large area of the body.
Nerve problems You may experience numbness or tingling sensation in the hands or feet. This side effect usually affects the fingertips and toes or soles of your feet after a few cycles of chemotherapy. This may be temporary and may improve after you finish treatment.	Inform your doctor if this symptom troubles you or affects your daily activities such as buttoning up shirts or picking up objects. Take extra care when walking or getting up if the numbness affects your feet, and when handling hot or sharp objects.
Muscle aches and/or joint pain	Mild pain can be relieved by taking Paracetamol. Inform your doctor if the pain does not get better. Do not take Paracetamol if you are having a fever at the same time. Taking regular warm baths may help.
Diarrhoea (loose and frequent stools)	Drink plenty of clear fluids (at least 2 litres or 8 glasses every day). Eat food that is gentler on the stomach such as porridge or soup. Avoid milk, dairy products, high-fibre food and oily or spicy food. Your doctor may prescribe medications to help relieve diarrhoea. Take these as instructed. Proceed to the A&E Department immediately if you have very bad diarrhoea (for example increase in bowel movement of more than 4 times per day) that does not improve even after taking medications for diarrhoea.
Increase in blood sugar levels Arsenic trioxide may cause raised blood sugar levels.	Your doctor may monitor your blood sugar levels more frequently and prescribe medications to control your blood sugar if required. For patients with diabetes, you may need to monitor your blood sugar regularly. See a doctor immediately if you have any symptoms of extremely high blood sugar. Signs of extremely high blood sugar include: Feeling confused or abnormally tired Often feeling extremely hungry or thirsty Passing urine a lot more often Abnormally fast breathing
Risk of secondary cancers	This occurs very rarely. Please discuss with your doctor if you have concerns.

What food or medication should I avoid when I take or use this medication?

Avoid eating any raw, uncooked or under-cooked food as your immunity is weakened.

Some medications can increase the risk of serious heart rhythm problems when taken together with Arsenic Trioxide. These include certain medications that affect the heart's electrical activity. If possible, these medications should be stopped or replaced with an alternative while you are on Arsenic Trioxide. If it is not possible to avoid taking them together, your heart will be monitored more closely.

Some medications can affect the levels of minerals (electrolytes) in your blood, which can increase the risk of heart rhythm problems. Avoid taking these medications together with Arsenic Trioxide where possible. If you must take them together, your electrolyte levels will be monitored more frequently.

Please consult your healthcare professional before using any other medications, including over-the-counter medicines, supplements and herbal products.

What else should I know about this medication?

Tips to help manage your condition while you are on arsenic trioxide.

Exercise	Light exercise is recommended as it helps to improve mobility, balance, and even emotional well-being. Avoid strenuous exercise, and rest when you are feeling tired.
Adequate hydration	Maintain adequate hydration with 2 to 3 litres of fluids per day unless you have been informed by your doctor to limit how much fluids you can drink. This will decrease your chances of getting constipation and prevent dehydration.
Medical and dental treatment	If you need to go to the hospital for any reason other than cancer, always inform the doctors and nurses that you are receiving anti-cancer treatment. Talk to your cancer doctor if you think you need dental treatment. Always inform your dentist that you are receiving anti-cancer treatment.
Seek support if you feel overwhelmed	It is normal to feel fearful or worried about your condition. Do not be afraid to talk about your concerns with your healthcare team or loved ones. There may be resources and support available to help you.

Disclaimer

Please take note that the above is not a complete list of all possible side-effects. If you have any concerns about your medication or if you have other side-effects that you think are caused by this medication, please consult your doctor or pharmacist. If you take more than the recommended dose, please seek medical advice immediately. The information provided on this page does not replace information from your healthcare professional. Please consult your healthcare professional for more information.

This article is jointly developed by members of the National Medication Information workgroup. The workgroup consists of cluster partners (NHG Health, National University Health System and SingHealth), community pharmacies (Guardian, Unity and Watsons) and Pharmaceutical Society of Singapore. The content does not reflect drug availability and supply information in pharmacies and healthcare institutions. You are advised to check with the respective institutions for such information.