The dosage is based on weight:

• less than 50 kg, the usual dose is: 120 mg twice a day.
• 50 kg or greater, the usual dose is: 160 mg twice a day. 

Selpercatinib is a tyrosine kinase inhibitor.  It is used to treat a specific type of non-small cell lung cancer (NSCLC) caused by altered RET protein kinase. RET altered proteins can lead to uncontrolled cell growth. Sepercatinib blocks the actions of the altered proteins and may slow or stop the cancer from growing.

Side effects that usually do not require medical attention unless bothersome:

• dry mouth
• diarrhea
• constipation
• nausea, abdominal pain, vomiting
• rash
• swelling of the ankles, hands, or feet

Side effects that you should report to your care team as soon as possible:

• Allergic reactions—skin rash, itching, hives, swelling of the face, lips, tongue, or throat
• Bleeding—bloody or black, tar-like stools, vomiting blood or brown material that looks like coffee grounds, red or dark brown urine, small red or purple spots on skin, unusual bruising or bleeding
• Dry cough, shortness of breath or trouble breathing
• Heart rhythm changes—fast or irregular heartbeat, dizziness, feeling faint or lightheaded, chest pain, trouble breathing
• Increase in blood pressure
• Liver injury—right upper belly pain, loss of appetite, nausea, light-colored stool, dark yellow or brown urine, yellowing skin or eyes, unusual weakness or fatigue
• Low thyroid levels (hypothyroidism)—unusual weakness or fatigue, increased sensitivity to cold, constipation, hair loss, dry skin, weight gain, feelings of depression
• Tumor lysis syndrome (TLS)—nausea, vomiting, diarrhea, decrease in the amount of urine, dark urine, unusual weakness or fatigue, confusion, muscle pain or cramps, fast or irregular heartbeat, joint pain

Because of some of the side effects caused by this medication, tell your healthcare provider if you have any of the following:

• Bleeding disorder
• Recent surgery
• High blood pressure
• Irregular heartbeat or rhythm
• Liver disease
• Lung disease
• Diabetes
• Stroke or brain injury
• Persistent vomiting
• An unusual or allergic reaction to selpercatinib, other medications, foods, dyes or preservatives

Drug interactions

Do not take this medication if you are on:

• Dronedarone
• Ketoconazole
• Pimozide
• Thioridazine

This medication may also interact with the following:

• Calcium channel blockers, such as diltiazem or verapamil
• Certain antivirals for HIV or hepatitis
• Certain medications for fungal infections like itraconazole, posaconazole
• Grapefruit juice
• Other medicines that cause heart rhythm changes
• Repaglinide
• Rifampin
• St. John's Wort
• Stomach acid blockers like cimetidine, famotidine, ranitidine, lansoprazole, omeprazole, pantoprazole

Use in pregnancy: This medication can cause serious birth defects if taken during pregnancy. A negative pregnancy test is required before starting this medication. A very effective form of birth control is recommended while taking this medication and for at least 2 weeks after stopping it.  If male individuals on this medication get a woman pregnant, there is potential for serious harm to the unborn child. Males must use highly effective birth control while on the medication and for at least 2 weeks after stopping it.

Use in breastfeeding: It is not known if selpercatinib passes into breast milk. Do not breastfeed during treatment and for at least 2 weeks after stopping it.