Common side effects of Selpercatinib include musculoskeletal pain, edema, diarrhea, fatigue, dry mouth, and hypertension. Different measures are taken depending on the severity of the side effects.

Common Adverse Reactions

Incidence (adult solid tumors, 25% and above): musculoskeletal pain 59%, edema 53%, diarrhea 52%, fatigue 49%, dry mouth 44%, hypertension 43%, abdominal pain 39%, rash 38%, nausea 36%, constipation 35%, cough 30%, headache 30%, vomiting 29%, dyspnea 28%, and hemorrhage 26%.

Record these symptoms and inform your doctor; do not suffer in silence or discontinue the medication on your own.

Laboratory Abnormalities (Side Effects Detected via Lab Tests)

Grade 3 to 4 laboratory abnormalities (adults, 5% and above): decreased lymphocytes 22%, increased ALT 13%, decreased sodium 13%, increased AST 11%, decreased calcium 7%, and decreased phosphate 5%. Additionally, there are others with higher overall incidence but lower proportions of severe cases: total increased AST 62%, decreased calcium 61%, decreased albumin 61%, total increased ALT 58%, increased glucose 56%, increased blood creatinine 51%, decreased sodium 49%, and increased alkaline phosphatase 43%.

Get blood tests drawn on schedule and undergo regular follow-ups. The median time to first elevation of liver enzymes is 4.9 to 5 weeks after starting treatment, so checking liver function every 2 weeks during the first 3 months of treatment is not excessive.

Serious Side Effects of Selpercatinib Requiring Immediate Medical Attention

Serious side effects of Selpercatinib that require high vigilance include hepatotoxicity (liver injury), interstitial lung disease/pneumonitis, hypertension, QT interval prolongation, hemorrhage, hypersensitivity (allergic reactions), and tumor lysis syndrome.

Side Effects Requiring Immediate Medical Attention

Hepatotoxicity (liver injury); interstitial lung disease / pneumonitis; hypertension; QT interval prolongation; hemorrhage; hypersensitivity / allergic reactions (including severe skin reactions); tumor lysis syndrome; impaired wound healing; hypothyroidism; and slipped capital femoral epiphysis (SCFE/SUFE) in pediatric patients.

Management of Side Effects

1. First, evaluate the severity of the side effects: Can you feel or notice them yourself? Are there warning signs such as fever, bleeding, jaundice, or shortness of breath?

2. If a serious side effect is suspected, seek immediate medical attention—do not wait.

3. If side effect symptoms are mild, record them and inform your doctor so they can be properly managed.

4. Do not reduce, increase, or stop the medication on your own. Rules in the prescribing information such as "withhold," "reduce by 2 dose levels," or "re-escalate by 1 level after 2 weeks without recurrence" are intended for physicians; please follow your doctor's instructions closely.

Friendly Reminder: Reporting side effects is inherently valuable. Every specific symptom you describe to your doctor (when it started, severity, whether it has improved) will influence subsequent dosage decisions.