Entrectinib Side Effects: What to Expect and When to Call Your Doctor

Like all cancer therapies, Entrectinib (Rozlytrek) comes with a range of potential side effects. Most are manageable with dose adjustments or supportive medications, but some require prompt medical attention. This guide covers what to expect, what warning signs to watch for, and how to manage the most common issues.

Common Side Effects of Entrectinib (Occurring in ≥20% of Patients)

In clinical trials, the following side effects were reported in 20% or more of patients taking Rozlytrek:

Fatigue (48%): The most common side effect. Can range from mild tiredness to significant functional impairment. Rest, pacing activities, and discussing dose adjustments with your oncologist can help.

Constipation (46%): Staying well hydrated, eating high-fiber foods, and using stool softeners or laxatives as recommended by your care team can help manage this.

Dysgeusia / taste changes (44%): Food may taste metallic, bitter, or different from normal. Experimenting with different foods, plastic utensils instead of metal, and zinc supplementation (discuss with your oncologist first) may help.

Edema / swelling (40%): Fluid retention causing swelling, most commonly in the legs, ankles, and feet. Elevating legs and limiting salt intake may help mild cases.

Dizziness (38%): Can affect balance and coordination. Avoid driving or operating heavy machinery until you know how this medication affects you.

Diarrhea (35%), Nausea (34%), Vomiting: Common GI effects. Taking the medication with food may help with nausea. Anti-nausea and anti-diarrheal medications can be prescribed by your oncologist if needed.

Dysesthesia (34%): Abnormal, often unpleasant sensations when touched or at rest — can feel like tingling, burning, or sensitivity. Notify your oncologist if these become severe.

Dyspnea / shortness of breath (30%), Cough: Report any new or worsening shortness of breath promptly, as it may indicate a serious cardiac side effect.

Cognitive impairment (memory, concentration): Sometimes called "chemo brain," this can include difficulty concentrating, memory lapses, and confusion. Tell your oncologist if these symptoms are affecting your daily function.

Weight gain, myalgia (muscle aches), arthralgia (joint pain), fever. Report any significant weight gain or severe muscle/joint pain to your oncologist.

Serious Side Effects: When to Seek Urgent Care

Rozlytrek has several serious side effects that require prompt medical evaluation. Contact your oncologist's office or go to the emergency room if you experience:

Congestive heart failure: Symptoms include shortness of breath, rapid weight gain, swelling in the legs/ankles, and fatigue. Your oncologist will monitor your left ventricular ejection fraction (LVEF) before and during treatment.

CNS effects: Severe confusion, hallucinations, mood changes, difficulty speaking, or loss of coordination. These require immediate medical attention.

Liver problems (hepatotoxicity): Yellowing of skin or eyes (jaundice), dark urine, severe right-sided abdominal pain, extreme fatigue. Liver function tests are monitored regularly.

Bone fractures: Rozlytrek can increase fracture risk. Report new bone pain, decreased range of motion, or any broken bone promptly.

QT prolongation / heart rhythm changes: Palpitations, fast or irregular heartbeat, fainting. Avoid other QT-prolonging drugs (including some antibiotics and anti-nausea medications — ask your oncologist).

High uric acid (hyperuricemia): Can trigger gout attacks. Symptoms include sudden severe joint pain, swelling, and redness, especially in the big toe.

Vision problems: Sudden vision changes, blurred vision, or eye pain. Keep all scheduled eye exams during treatment.

Important Safety Notes

Pregnancy: Entrectinib can cause serious harm to a developing fetus. Use effective contraception during treatment and for at least 5 weeks after the last dose (females). Males should use contraception for 3 months after the last dose.

Breastfeeding: Do not breastfeed during treatment or for 7 days after the last dose.

Grapefruit: Avoid grapefruit and grapefruit juice entirely during treatment, as they can increase entrectinib blood levels and worsen side effects.

Driving: Avoid driving or operating heavy machinery until you know how entrectinib affects your alertness and coordination, given the risk of dizziness and cognitive effects.

The Bottom Line

Most patients on entrectinib experience some side effects, but many are manageable. The key is communication with your oncologist — don't dismiss symptoms as trivial. Report anything new or worsening. For related reading, see our guide to entrectinib drug interactions. And if you need help finding a pharmacy that stocks your medication, medfinder is here to help.