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Enhertu Side Effects

Generic name: fam-trastuzumab deruxtecan

Medically reviewed by Philip Thornton, DipPharm. Last updated on Jul 28, 2022.

Note: This document contains side effect information about fam-trastuzumab deruxtecan. Some dosage forms listed on this page may not apply to the brand name Enhertu.

Applies to fam-trastuzumab deruxtecan: intravenous powder for solution.


Intravenous route (Powder for Solution)

Interstitial Lung Disease (ILD) and pneumonitis, including fatal cases, have been reported. Monitor for and promptly investigate signs and symptoms including cough, dyspnea, fever, and other new or worsening respiratory symptoms. Permanently discontinue in all patients with Grade 2 or higher ILD/pneumonitis. Advise patients of the risk and the need to immediately report symptoms. Exposure to fam-trastuzumab deruxtecan-nxki during pregnancy can cause embryo-fetal harm. Advise patients of these risks and the need for effective contraception.

Serious side effects of Enhertu

Along with its needed effects, fam-trastuzumab deruxtecan (the active ingredient contained in Enhertu) 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 or nurse immediately if any of the following side effects occur while taking fam-trastuzumab deruxtecan:

More common

  • Black, tarry stools
  • bloody nose
  • bone or muscle pain
  • burning, numbness, tingling, or painful sensations
  • chest pain or tightness
  • chills
  • cough
  • decreased urine output
  • difficult breathing
  • dilated neck veins
  • dry mouth
  • fever
  • general feeling of discomfort or illness
  • increased thirst
  • irregular breathing
  • irregular heartbeat
  • loss of appetite
  • lower back or side pain
  • mood changes
  • muscle cramps
  • nausea or vomiting
  • numbness or tingling in the hands, feet, or lips
  • painful or difficult urination
  • pale skin
  • seizures
  • sneezing
  • sore throat
  • swelling of the face, fingers, feet, or lower legs
  • thickening of bronchial secretions
  • trouble breathing
  • ulcers, sores, or white spots in the mouth
  • unsteadiness or awkwardness
  • unusual bleeding or bruising
  • unusual tiredness or weakness
  • weakness in the arms, hands, legs, or feet
  • weight gain

Other side effects of Enhertu

Some side effects of fam-trastuzumab deruxtecan 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

Less common

  • Bloated
  • change in taste
  • darkening of the skin
  • excess air or gas in the stomach or intestines
  • full feeling
  • loss of taste
  • passing gas

Incidence not known

  • Bleeding, blistering, burning, coldness, discoloration of the skin, feeling of pressure, hives, infection, inflammation, itching, lumps, numbness, pain, rash, redness, scarring, soreness, stinging, swelling, tenderness, tingling, ulceration, or warmth at the injection site

For Healthcare Professionals

Applies to fam-trastuzumab deruxtecan: intravenous powder for injection.


Very common (10% or more): Anemia (e.g., anemia, hemoglobin decreased, hematocrit decreased, red blood cell count decreased) (31%), neutropenia (e.g., neutropenia, neutrophil count decreased) (30%), leukopenia (e.g., leukopenia, lymphopenia, white blood cell count decreased) (22%), thrombocytopenia (e.g., thrombocytopenia, platelet count decreased) (20%)[Ref]


Frequency not reported: As with all therapeutic proteins there is potential for immunogenicity[Ref]


Very common (10% or more): Dry eye (11%)[Ref]


Very common (10% or more): Decreased appetite (32%), hypokalemia (12%)[Ref]


Very common (10% or more): Aspartate aminotransferase increased (14%), alanine aminotransferase increased (14%)[Ref]


Very common (10% or more): Cough (20%), dyspnea (13%), epistaxis (13%)

Common (1% to 10%): Interstitial lung disease (ILD) (e.g., pneumonitis, ILD, respiratory failure, organizing pneumonia, acute respiratory failure, lung infiltration, lymphangitis, alveolitis), upper respiratory tract infection (e.g., influenza, influenza like illness, upper respiratory tract infection) (15%)[Ref]


Very common (10% or more): Fatigue/asthenia (59%)[Ref]

Nervous system

Very common (10% or more): Headache (e.g., headache, sinus headache, migraine) (19%)[Ref]


Frequency not reported: Left ventricular dysfunction (LVEF)[Ref]


Very common (10% or more): Alopecia (46%), rash (e.g., rash, rash pustular, rash maculopapular) (10%)[Ref]


Very common (10% or more): Nausea (79%), vomiting (47%), constipation (35%), diarrhea (29%), abdominal pain (e.g., abdominal discomfort, GI pain, abdominal pain, abdominal pain lower, abdominal pain upper) (19%), stomatitis (e.g., stomatitis, aphthous ulcer, mouth ulceration, oral mucosa erosion, oral mucosa blistering) (14%), dyspepsia (12%)[Ref]

Frequently asked questions


1. "Product Information. Enhertu (fam-trastuzumab deruxtecan)." Daiichi Sankyo, Inc. (2020):

2. "Product Information. Enhertu (fam-trastuzumab deruxtecan)." Daiichi Sankyo, Inc. (2019):

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.