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Selumetinib Side Effects

Medically reviewed by Last updated on April 27, 2020.

For the Consumer

Applies to selumetinib: oral capsule


Follow all directions on your medicine label and package. Tell each of your healthcare providers about all your medical conditions, allergies, and all medicines you use.

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

  • severe or ongoing diarrhea;

  • a skin rash with blistering or peeling, or any rash that covers a large area of skin;

  • heart problems--tiredness, fast heartbeats, cough, wheezing, shortness of breath, swelling in your lower legs;

  • vision changes--blurred vision, vision loss, seeing dark spots or "floaters" in your vision;

  • unexplained muscle pain, tenderness, or weakness (especially if you also have fever, unusual tiredness, or dark colored urine).

Diarrhea is a common side effect of this medicine. Tell your doctor right away the first time you have diarrhea while taking selumetinib.

Your doses may be delayed or permanently discontinued if you have certain side effects.

Common side effects may include:

  • nausea, vomiting, stomach pain;

  • itching;

  • dry skin, acne, rash;

  • redness around your fingernails;

  • feeling weak or tired;

  • mouth pain or soreness, swollen gums;

  • muscle or bone pain;

  • headache; or

  • fever.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.

For Healthcare Professionals

Applies to selumetinib: oral capsule


Very common (10% or more): Hemoglobin decreased (41%), neutrophils decreased (33%), lymphocytes decreased (20%)

Frequency not reported: Increased vitamin E causing increased bleeding[Ref]


Very common (10% or more): Creatinine phosphokinase (CPK) increased (79%), musculoskeletal pain (e.g., pain in extremity, back pain, neck pain, musculoskeletal pain) (58%)[Ref]


Very common (10% or more): Blurred vision, photophobia, cataracts, and ocular hypertension (15%), visual impairment

Frequency not reported: Retinal vein occlusion (RVO), retinal pigment epithelial detachment (RPED)[Ref]


Very common (10% or more): Albumin decreased (79%), anorexia (22%), increased/decreased potassium (18%), amylase increased (18%), sodium increased (18%), sodium decreased (16%), weight increased[Ref]


Very common (10% or more): Hematuria (22%), proteinuria (22%)[Ref]


Very common (10% or more): AST increased (41%), ALT increased (35%), alkaline phosphatase increased (18%), acute kidney injury[Ref]


Very common (10% or more): Epistaxis (28%), dyspnea (e.g., exertional dyspnea, dyspnea at rest)[Ref]


Very common (10% or more): Fatigue/malaise (56%), pyrexia (56%), edema (e.g., peripheral swelling, edema, localized edema) (20%), edema (e.g., periorbital edema, face edema)[Ref]


The most common adverse reactions (40% or greater) were vomiting, rash (all), abdominal pain, diarrhea, nausea, dry skin, fatigue, musculoskeletal pain, pyrexia, acneiform rash, stomatitis, headache, paronychia, and pruritus.[Ref]

Nervous system

Very common (10% or more): Headache (48%)[Ref]


Very common (10% or more): Cardiomyopathy (decrease in left ventricular ejection fraction [LVEF] greater than or equal to 10% below baseline) (22%), sinus tachycardia (20%), hypertension[Ref]


Very common (10% or more): Rash (e.g., dermatitis acneiform, rash maculopapular, erythema, rash pustular, urticaria, exfoliative rash, rash pruritic, rash erythematous, eczema) (91%), dry skin (60%), rash acneiform (dermatitis acneiform) (50%), paronychia (e.g., paronychia, nail infection) (48%), pruritus (46%), dermatitis (e.g., dermatitis, dermatitis atopic, dermatitis diaper, eczema, seborrheic dermatitis, skin irritation) (36%), hair changes (e.g., alopecia, hair color change) (32%)

Frequency not reported: Palmar-plantar erythrodysesthesia syndrome[Ref]


Very common (10% or more): Vomiting (82%), abdominal pain (76%), diarrhea (70%), nausea (66%), stomatitis (e.g., stomatitis, mouth ulceration) (50%), constipation (34%), lipase increased (32%), dry mouth, GI perforation, colitis, ileus, intestinal obstruction[Ref]


1. "Product Information. Koselugo (selumetinib)." Astra-Zeneca Pharmaceuticals, Wilmington, DE.

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.