See also How to Use section.

Nausea, vomiting, or diarrhea may occur. Nausea and vomiting can be severe. In some cases, your doctor may prescribe medication to prevent or relieve nausea and vomiting. Eating several small meals, not eating before treatment, or limiting activity may help lessen some of these effects. If these effects last or get worse, tell your doctor or pharmacist promptly.

Temporary hair loss is another common side effect. Normal hair growth should return after treatment has ended.

Many people using this medication may have serious side effects. However, you have been prescribed this drug because your doctor has judged that the benefit to you is greater than the risk of side effects. Careful monitoring by your doctor may decrease your risk. Serious side effects may not happen until days to weeks after your treatment.

Pain/sores in the mouth and throat may occur. Brush your teeth gently/carefully, avoid using mouthwash that contains alcohol, and rinse your mouth often with cool water mixed with baking soda or salt. It may also be best to eat soft, moist foods. Tell your doctor right away if these effects last or get worse or if you have trouble swallowing.

Tell your doctor right away if you have any serious side effects, including: unusual weight gain, signs of liver problems (nausea/vomiting that doesn't stop, loss of appetite, stomach/abdominal pain, yellowing eyes/skin, dark urine), signs of kidney problems (such as change in the amount of urine, painful/difficult urination, red/pinkish urine).

This medication decreases bone marrow function, an effect that may lead to a low number of blood cells such as red cells, white cells, and platelets. This effect can cause anemia, decrease your body's ability to fight an infection, or cause easy bruising/bleeding. Tell your doctor right away if you develop any of the following unlikely symptoms: unusual tiredness, pale skin, signs of infection (such as sore throat that doesn't go away, fever, chills), easy bruising/bleeding.

Dactinomycin may increase the risk of other cancers (such as leukemia). Consult your doctor for more details.

When dactinomycin is given after radiation treatment, it can sometimes cause a serious skin reaction that looks likes a severe sunburn (radiation recall). The reaction usually develops within days to months after treatment on the skin area previously treated with radiation. Throat problems can also be part of radiation recall with dactinomycin. Tell your doctor right away if you develop skin redness/tenderness/swelling/peeling/blisters or painful/difficult swallowing. If you develop a skin reaction, avoid prolonged sun exposure, tanning booths, and sunlamps. Use a sunscreen and wear protective clothing when outdoors.

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.