See also Warning section.
Diarrhea, redness/irritation at the injection site, dizziness, muscle/joint/back pain, stomach/abdominal pain, constipation, trouble sleeping, nausea, vomiting, mouth sores, dry mouth, changes in taste, and loss of appetite 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 any of these effects persist or worsen, tell your doctor or pharmacist promptly.
Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
Tell your doctor right away if you have any serious side effects, including: bone pain, increased coughing, trouble breathing, swelling of the hands/ankles/feet, unusual tiredness, severe headache, tingling/numbness (such as in the hands, feet, leg), mental/mood changes, fast/pounding heartbeat, muscle cramps, easy bruising/bleeding.
Get medical help right away if you have any very serious side effects, including: weakness on one side of the body, slurred speech, vision changes, confusion.
This medication may lower your ability to fight infections. This may make you more likely to get a serious (rarely fatal) infection or make any infection you have worse. Tell your doctor right away if you have any signs of infection (such as fever, chills, persistent sore throat, cough).
This medication can sometimes cause a serious infusion reaction with serious lung problems. Immediately tell your doctor of the following side effects that occur while this drug is being given or within 24 hours after your treatment is finished, such as chills, fever, flushing, wheezing, shortness of breath, nausea, headache, dizziness, fainting, rash, and weakness.
Ado-trastuzumab emtansine can commonly cause a rash that is usually not serious. However, you may not be able to tell it apart from a rare rash that could be a sign of a severe reaction. Therefore, tell your doctor immediately if you develop any rash.
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.
In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.