What the label lists and what reports show
Selumetinib side effects
Selumetinib's FDA label: “Most common adverse reactions in pediatric patients (≥ 40%) are: vomiting, diarrhea, increased creatine phosphokinase, dry skin, paronychia, nausea, dermatitis acneiform, and pyrexia.” FAERS holds 1,530 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is rash (128 reports).
- No generic listed
Check it at the source: the selumetinib FDA label on DailyMed (effective May 26, 2026, AstraZeneca Pharmaceuticals LP); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of KOSELUGO?KOSELUGO can cause serious side effects, including: • Heart problems. KOSELUGO can lower the amount of blood pumped by your heart, which can be severe. Your healthcare provider will do tests before and during treatment with KOSELUGO to check how well your heart is working. Tell your healthcare provider right away if you get any of the following signs or symptoms: ∘ persistent coughing or wheezing ∘ shortness of breath ∘ swelling of your ankles and feet ∘ tiredness ∘ increased heart rate • Eye problems. KOSELUGO can cause eye problems that can lead to blindness. Your healthcare provider will check your vision before and during treatment with KOSELUGO. […]
Source: FDA drug label, AstraZeneca Pharmaceuticals LP, effective May 26, 2026 (SPL set 7d042c61-f28f-4ab5-ab10-d7558c0d49ff), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsMost common adverse reactions in pediatric patients (≥ 40%) are: vomiting, diarrhea, increased creatine phosphokinase, dry skin, paronychia, nausea, dermatitis acneiform, and pyrexia.
Table 10 Adverse Reactions (≥ 20%) in Patients Who Received KOSELUGO in SPRINT Phase II Stratum 1
| Reaction | Adverse Reaction All Grades (%) | KOSELUGO (N = 50) Grade ≥ 3 (%) * |
|---|---|---|
| Vomiting | 82 | 6 |
| Abdominal pain Abdominal pain includes abdominal pain; abdominal pain upper | 76 | 0 |
| Diarrhea | 70 | 16 |
| Nausea | 66 | 2 |
| Stomatitis Stomatitis includes stomatitis; mouth ulceration | 50 | 0 |
| Constipation | 34 | 0 |
| Rash (all) Rash (all) includes dermatitis acneiform; rash maculo-papular; erythema; rash… | 80 | 6 |
| Dry skin | 60 | 0 |
| Rash acneiform Rash (acneiform) includes dermatitis acneiform | 50 | 4 |
| Paronychia Paronychia includes paronychia; nail infection | 48 | 6 |
| Pruritus | 46 | 0 |
| Dermatitis Dermatitis includes dermatitis; dermatitis atopic; dermatitis diaper; eczema;… | 36 | 4 |
| Hair changes Hair changes include alopecia; hair color change | 32 | 0 |
| Musculoskeletal pain Musculoskeletal pain includes pain in extremity; back pain; neck… | 58 | 0 |
| Fatigue Fatigue includes fatigue; malaise | 56 | 0 |
| Pyrexia | 56 | 8 |
| Edema Edema includes peripheral swelling; edema; localized edema | 20 | 0 |
| Headache | 48 | 2 |
| Epistaxis | 28 | 0 |
| Hematuria | 22 | 2 |
| Proteinuria | 22 | 0 |
| Decreased appetite | 22 | 0 |
| Decreased ejection fraction | 22 | 0 |
| Sinus tachycardia | 20 | 0 |
| Skin infection Skin infection includes skin infection; abscess; cellulitis; impetigo;… | 20 | 2 |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedThe following clinically significant adverse reactions are described elsewhere in the labeling: • Left Ventricular Dysfunction [see Warnings and Precautions (5.1) ] • Ocular Toxicity [see Warnings and Precautions (5.2) ] • Gastrointestinal Toxicity [see Warnings and Precautions (5.3) ] • Skin Toxicity [see Warnings and Precautions (5.4) ] • Increased Creatine Phosphokinase [see Warnings and Precautions (5.5) ] Most common adverse reactions in pediatric patients (≥ 40%) are: vomiting, diarrhea, increased creatine phosphokinase, dry skin, paronychia, nausea, dermatitis acneiform, and pyrexia. ( 6.1 ) Most common adverse reactions in adult patients (≥ 40%) are rash (all), dermatitis acneiform, and diarrhea. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact AstraZeneca 1-800-236-9933 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. …
Source: FDA drug label, AstraZeneca Pharmaceuticals LP, effective May 26, 2026 (SPL set 7d042c61-f28f-4ab5-ab10-d7558c0d49ff), via openFDA; the full label on DailyMed
What do FAERS reports show?
1,530 reports list selumetinib among the medicines taken, each a report of something that happened, not proof the medicine caused it; 99 are coded as a death and 289 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 21 reactions below, 16 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Selumetinib: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions