Retevmo (Selpercatinib) - Uses, Side Effects, and More

What are the most common side effects of Retevmo?

The most common side effects of Retevmo in adults are listed below. Tell your health care provider if you have any of these side effects that bother you.

• Muscle or joint pain
• Fluid retention
• Diarrhea
• Tiredness
• Dry mouth
• Increased blood pressure (see below)
• Stomach pain
• Rash
• Nausea and vomiting
• Constipation
• Cough
• Headache
• Shortness of breath
• Bleeding (see below)
• Decreased white blood cells
• Changes in liver function tests
• Decreased sodium, calcium, and phosphate levels

The most common side effects of Retevmo in children who are 2 years of age or older are listed below. Tell your health care provider if you have any of these side effects that bother you.

• Muscle or bone pain
• Diarrhea
• Nausea and vomiting
• Bleeding (see below)
• Fever
• Stomach pain
• Headache
• Tiredness
• Cough
• Rash
• Infection in the nose or throat, sore throat, or common cold symptoms 
• Fluid retention
• Decreased calcium, magnesium, and potassium levels
• Blood disorders, such as low hemoglobin (red blood cells) and low white blood cell levels (leukopenia)

There may be other side effects of Retevmo that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088 (800-332-1088). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of Retevmo?

While less common, the most serious side effects of Retevmo are described below, along with what to do if they happen.

Severe Allergic Reactions. Retevmo may cause allergic reactions, including serious skin reactions such as Stevens-Johnson syndrome (SJS). Stop taking Retevmo and get help right away if you have any of the following symptoms of a serious allergic reaction.

• Breathing problems or wheezing
• Racing heart
• Fever or general ill feeling
• Swollen lymph nodes
• Swelling of the face, lips, mouth, tongue, or throat
• Trouble swallowing or throat tightness
• Itching or skin rash
• Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
• Nausea or vomiting
• Dizziness, feeling lightheaded, or fainting
• Stomach cramps
• Joint pain

Liver Damage. Liver damage, also called hepatotoxicity, can happen when taking Retevmo. Call your health care provider right away if you have any of the following symptoms of liver damage.

• Nausea or vomiting
• Stomach or belly pain
• Fever
• Weakness or unusual tiredness
• Itching
• Loss of appetite
• Light-colored poop
• Dark-colored urine (pee)
• Your skin or the whites of your eyes turning yellowish in color (also called jaundice)

Lung Inflammation. Retevmo can cause inflammation in your lungs, also called interstitial lung disease or pneumonitis. This can be dangerous and life-threatening. Get emergency help if you have any new or worsening trouble breathing. You may also have a cough, fever, or chest pain. 

Increased Blood Pressure (Hypertension). Retevmo may increase your blood pressure or make it worse if you have a history of high blood pressure. Call your health care provider if your blood pressure increases while taking this medicine.

If you measure your blood pressure and the top number (systolic) is 180 mm Hg or higher or the bottom number (diastolic) is 120 mm Hg or higher, get medical attention right away. Increases in blood pressure may not be noticeable but look out for any of the following symptoms of severely high blood pressure.

• Sudden severe headache
• Chest pain
• Dizziness or confusion
• Trouble breathing
• Nausea/vomiting
• Blurry or other changes to vision
• Anxiety
• Buzzing in the ears
• Nosebleed
• Feeling of skipped heartbeats

Heart Rhythm Changes. Retevmo may cause a rare, dangerous heart rhythm problem called QT prolongation and torsade de pointes. Some people have a higher risk of this, including people who are older, have other people in their family who have had these conditions, have low potassium or magnesium levels, or who take some medicines for other heart rhythm problems. Tell your health care provider right away if you faint or have changes in your heart rate or rhythm, such as a fast or skipping heartbeat.

Bleeding. Retevmo can increase your risk of severe bleeding that can lead to death. Some people with serious bleeding may need a blood transfusion or surgery. Call your health care provider right away if you have any of the following signs of severe bleeding while taking Retevmo.

• Pink, red, or brown urine (pee)
• Vomit with blood that looks like coffee grounds
• Red or black stools (looks like tar)
• Coughing up blood or blood clots

Tumor Lysis Syndrome. Retevmo can cause a fast breakdown of cancer cells. This can lead to a condition called tumor lysis syndrome, which can be serious. It is important to drink plenty of water while taking Retevmo and to keep all appointments for blood work so your health care provider can see how your body is responding to the medicine. Tell your health care provider right away if you have any of the following signs of tumor lysis syndrome. 

• Nausea and vomiting
• Weakness
• Swelling or fluid retention
• Shortness of breath
• Muscle cramps 
• Seizures

Wound Healing Issues. Retevmo can make it harder for your body to heal wounds. Tell your health care provider if you have any planned or emergency surgeries or if you have any injuries that occur while taking Retevmo. Usually they will tell you to stop taking Retevmo at least 7 days before your surgery, but your health care provider will tell you when you should stop taking Retevmo based on your surgery and treatment. 

Low Thyroid Hormones (Hypothyroidism). Retevmo can cause the function of your thyroid gland to change, which can lead to low thyroid levels. Attend all of your appointments for blood work so your health care provider can see how your thyroid is responding to Retevmo. Tell your health care provider right away if you have any of the following signs of low thyroid hormones. 

• Weight gain
• Feeling cold 
• Tiredness that does not go away or continues to worsen
• Constipation

Hip Joint Problems. Retevmo can cause hip joint problems in children. These included a slipped capital femoral epiphysis or a slipped upper femoral epiphysis. Tell your health care provider right away if you or your child have any signs of hip problems, including hip and knee pain or a limp without pain.