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Tucatinib Side Effects

Medically reviewed by Last updated on May 14, 2021.

For the Consumer

Applies to tucatinib: oral tablet

Side effects requiring immediate medical attention

Along with its needed effects, tucatinib may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking tucatinib:

More common

  • Bloody nose
  • burning, numbness, tingling, or painful sensations
  • clay colored stools
  • dark urine
  • decreased or loss of appetite
  • fever
  • headache
  • mood or mental changes
  • nausea and vomiting
  • pale skin
  • severe diarrhea
  • skin rash, itching
  • swelling of the feet or lower legs
  • stomach pain or tenderness
  • troubled breathing with exertion
  • unsteadiness or awkwardness
  • unusual bleeding or bruising
  • unusual tiredness or weakness
  • weakness of the arms, hands, legs, or feet
  • yellow eyes or skin

Less common

  • Muscle spasm or jerking of all extremities
  • loss of bladder control
  • seizures
  • sudden loss of consciousness

Side effects not requiring immediate medical attention

Some side effects of tucatinib may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

  • Difficulty in moving
  • loss of weight
  • muscle pain or stiffness
  • pain in the joints
  • redness, swelling, pain of the skin
  • scaling of the skin on the hands and feet
  • swelling or inflammation of the mouth
  • ulceration of the skin

For Healthcare Professionals

Applies to tucatinib: oral tablet


Very common (10% or more): Hemoglobin decreased (59%), decreased phosphate (57%), anemia (e.g., anemia, hemoglobin decreased, normocytic anemia) (21%)[Ref]


Very common (10% or more): Arthralgia (15%)[Ref]


Very common (10% or more): Anorexia (25%), weight loss (13%), magnesium decreased (40%), potassium decreased (36%), alkaline phosphate increased (26%)[Ref]


Very common (10% or more): Bilirubin increased (47%), ALT increased (46%), AST increased (43%), hepatotoxicity (e.g., hyperbilirubinemia, blood bilirubin increased, bilirubin conjugated increased, alanine aminotransferase increased, transaminases increased, hepatotoxicity, aspartate aminotransferase increased, liver function test increased, liver injury, hepatocellular injury) (42%)[Ref]


Very common (10% or more): Creatinine increased (33%)[Ref]


Very common (10% or more): Palmar-plantar erythrodysesthesia syndrome (63%), rash (e.g., rash maculopapular, rash, dermatitis acneiform, erythema, rash macular, rash papular, rash pustular, rash pruritic, rash erythematous, skin exfoliation, urticaria, dermatitis allergic, palmar erythema, plantar erythema, skin toxicity, dermatitis) (20%)[Ref]


Very common (10% or more): Diarrhea (81%), nausea (58%), vomiting (36%), stomatitis (e.g., stomatitis, oropharyngeal pain, oropharyngeal discomfort, mouth ulceration, oral pain, lip ulceration, glossodynia, tongue blistering, lip blister, oral dysesthesia, tongue ulceration, aphthous ulcer) (32%)[Ref]

Frequently asked questions


1. "Product Information. Tukysa (tucatinib)." Seattle Genetics Inc, Bothell, WA.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.