Arsenic trioxide (Trisenox®)

Author: OncoLink Team
Content Contributor: Allyson Van Horn, MPH
Last Reviewed: August 21, 2026

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Pronounce: AR-se-nik trye-OX-ide

Classification: Antineoplastic Agent

About Arsenic trioxide (Trisenox®)

This medication is a form of the naturally occurring compound arsenic. It has been used by health practitioners (particularly in Asia) for hundreds of years. It is safe when given in small doses by experienced healthcare professionals. It seems to work against cancer by causing cancer cells to self-destruct; this is also known as apoptosis.

How to Take This Medication

This medication is given by intravenous (into a vein) infusion. Your specific dose will depend on your body size. Your treatment schedule will depend on where you are in your treatment course.

Possible Side Effects

These are some of the most common or most serious side effects of this medication. Talk with your provider about the side effects you are having and how they can be managed.

Differentiation Syndrome

Differentiation syndrome is when there is a large, fast release of certain proteins from your immune system. These proteins, called cytokines, are released into your bloodstream. This can cause symptoms such as:

  • A fever. Call for a temperature over 100.4°F or 38°C or as directed by your provider.
  • Sudden weight gain.
  • Bone or joint pain.
  • Fluid build-up around your heart, lungs, and/or chest, causing shortness of breath.

You may be given medications to help treat this syndrome. Your provider will watch closely for these signs and symptoms, which often start within 2 weeks of starting treatment, but can happen as long as 6 months after treatment. Tell your provider right away if you have any of these symptoms

Heart Issues

This medication can cause slow or abnormal heartbeats or an abnormal heart rhythm called QT prolongation. You will be monitored prior to and during treatment with electrocardiograms. In some cases this medication can also cause a faster than normal heartbeat. Notify your provider right away if you feel abnormal heartbeats, chest pain or if you feel dizzy or faint.

Encephalopathy

This medication can cause an inflammation of the brain, also called encephalopathy. You should contact your provider right away for any symptoms such as confusion, decreased level of consciousness, seizures, changes in how you are thinking, trouble walking, or changes in your vision or hearing.

Nausea and/or Vomiting

Talk to your providers if you have nausea and/or vomiting. They can prescribe medications to help you. Making changes to your diet can also help. Avoid things that make your symptoms worse, like heavy or greasy/fatty foods and spicy or acidic foods, like tomatoes, lemons, and oranges. Try saltines or ginger ale to help your symptoms.  

Call your providers if you cannot keep fluids down for more than 12 hours or if you feel lightheaded or dizzy.

Fatigue

Fatigue can cause exhaustion, feeling worn out and that your body is "heavy" and hard to move, or being unable to focus. It is common when you have cancer, and it is not the same as feeling tired. You may need to adjust your schedule to manage fatigue. Plan times to rest during the day and save your energy for more important activities. Exercise can help lessen fatigue. Talk to your providers about ways to deal with this side effect.

Muscle or Joint Pain/Aches and Headache

You may have joint or muscle pain/aches and headaches while taking this medication. Your provider can recommend medications and other ways to help relieve your pain.

Diarrhea

Diarrhea is when you pass three or more stools in a day. Your providers can suggest medications to relieve diarrhea. Do not take any medications to manage your diarrhea without talking to your provider first, as your stool may need to be tested. To manage it, try eating foods that are low in fiber and bland, like white rice and boiled or baked chicken. Try not to eat raw fruits, vegetables, whole grain breads, cereals, and seeds. Soluble fiber is a type of fiber found in some foods that helps absorb (soak up) fluid. Foods high in soluble fiber are applesauce, bananas (ripe), canned fruit, oranges, boiled potatoes, white rice, foods made with white flour, oatmeal, cream of rice, cream of wheat, and farina. Stay hydrated by drinking 8 to 10 glasses of non-alcoholic, non-caffeinated fluid each day.

Electrolyte Abnormalities

This medication can affect your electrolytes (potassium, magnesium, sodium, calcium, etc.). Your electrolyte levels will be checked with blood tests. If your levels get too low, you may be given electrolytes by IV (intravenously through your vein) or by mouth. Talk to your provider before taking any supplements. 

Leukocytosis (high white blood cell count)

This medication can impact your white blood cell counts. Generally, it does not cause any problems, nor does it require stopping the treatment. Your provider will monitor your white blood count during treatment.

High Blood Sugar

This medication can cause high blood sugar in patients with and without diabetes. Symptoms can be:

  • Feeling more thirsty.
  • More frequent urination.
  • Feeling hungrier. 
  • Blurry vision.
  • Headaches.
  • Breath smelling like fruit.

All patients will have their blood sugar checked with blood tests. If you have diabetes and your blood sugars are higher than normal, talk to your provider. Tell your provider if you have any of these symptoms.

Rash

Some people may get a rash, scaly skin, or red, itchy bumps from this medication. Tell your provider if you notice any of these changes in your skin, since it could be a reaction. Your provider may suggest:

  • Using an alcohol-free moisturizer on your skin and lips, and do not use moisturizers with perfumes or scents. 
  • Keep the area clean to avoid infection, especially if it cracks or bleeds.
  • Using a topical medication (applied to the skin) if the itching bothers you.

Be sure to talk with your provider about how to care for your skin.

Edema (Swelling)

This medication can cause swelling. If you experience rapid weight gain or swelling in your legs or feet, notify your provider.

Reproductive Concerns

There is a higher risk of health problems for your baby if you are pregnant, become pregnant, or get someone pregnant while on this medication. To lower the risk of birth defects, you should use birth control (contraception) to avoid pregnancy. Talk with your provider about what kind of birth control is safest for you and your partner.

If you can become pregnant, you will need to use effective birth control during treatment and for 6 months after the last dose of this medication, even if your menstrual cycle has stopped or changed. If you can get someone pregnant, you will need to use effective birth control during treatment and for 3 months after the last dose of this medication, even if you believe you are not producing sperm. You should not breastfeed during treatment and for 2 weeks after the last dose of this medication.

Important but Less Common Side Effects

Allergic Reactions

Some people may have an allergic reaction to this medication. Signs of an allergic reaction are:

  • Shortness of breath or trouble breathing.
  • Chest pain.
  • Rash.
  • Itching.
  • Flushing (reddening of the skin, often on the face, neck, or chest).
  • A drop in blood pressure (you may feel lightheaded, dizzy, or weak).

If you have any of these signs while you are getting an infusion, tell your provider right away. The infusion will be slowed down or stopped. Depending on your reaction, you may still be able to get the medication if you are given medicine to prevent a reaction or if the medication is given at a slower rate.

Secondary Cancers

A secondary cancer happens as a result of cancer treatment for another cancer. This is rare, but you should know your risk. Secondary cancers can be related to chemotherapy and other anti-cancer medications. Often, a secondary cancer is a blood cancer. This can happen years after treatment and is often related to repeated treatments or high doses. Your provider will watch your labs closely. They may suggest you have a blood test called a complete blood count with differential. This is often done each year if you had high risk therapies.

Liver Toxicity

This medication can cause liver toxicity, or liver problems, which your provider may monitor for with blood tests called liver function tests. Symptoms may be:

  • Yellowing of your skin or eyes.
  • Dark or brown urine.
  • Pain in your abdomen (belly).

Tell your provider if you have any of these symptoms.