What the label lists and what reports show
Irinotecan side effects
Irinotecan's FDA label: “The most common reasons for dose reduction were late diarrhea, neutropenia, and leukopenia.” FAERS holds 12,786 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 diarrhoea (1,722 reports).
- Generic listed
- A presentation discontinued
- Boxed warning
Check it at the source: the irinotecan FDA label on DailyMed (effective May 12, 2026, Pharmacia & Upjohn Company LLC); the FDA FAERS public dashboard.
What does the label list?
From the label: adverse reactionsThe most common reasons for dose reduction were late diarrhea, neutropenia, and leukopenia.
Table 5. Study 1: Percent (%) of Patients Experiencing Clinically Relevant Adverse Events in Combination Therapies Severity of adverse events based on NCI CTC (version 1.0)
| Reaction | Grade 1–4 | Grade 3&4 | Grade 1–4 | Grade 3&4 | Grade 1–4 | Grade 3&4 |
|---|---|---|---|---|---|---|
| TOTAL Adverse Events | 100 | 53.3 | 100 | 45.7 | 99.6 | 45.7 |
| Late | 84.9 | 22.7 | 69.4 | 13.2 | 83.0 | 31.0 |
| Early | 45.8 | 4.9 | 31.5 | 1.4 | 43.0 | 6.7 |
| Nausea | 79.1 | 15.6 | 67.6 | 8.2 | 81.6 | 16.1 |
| Abdominal pain | 63.1 | 14.6 | 50.2 | 11.5 | 67.7 | 13.0 |
| Vomiting | 60.4 | 9.7 | 46.1 | 4.1 | 62.8 | 12.1 |
| Anorexia | 34.2 | 5.8 | 42.0 | 3.7 | 43.9 | 7.2 |
| Constipation | 41.3 | 3.1 | 31.5 | 1.8 | 32.3 | 0.4 |
| Mucositis | 32.4 | 2.2 | 76.3 | 16.9 | 29.6 | 2.2 |
| Neutropenia | 96.9 | 53.8 | 98.6 | 66.7 | 96.4 | 31.4 |
| Leukopenia | 96.9 | 37.8 | 98.6 | 23.3 | 96.4 | 21.5 |
| Anemia | 96.9 | 8.4 | 98.6 | 5.5 | 96.9 | 4.5 |
| Thrombocytopenia | 96.0 | 2.6 | 98.6 | 2.7 | 96.0 | 1.7 |
| Asthenia | 70.2 | 19.5 | 64.4 | 11.9 | 69.1 | 13.9 |
| Pain | 30.7 | 3.1 | 26.9 | 3.6 | 22.9 | 2.2 |
| Fever | 42.2 | 1.7 | 32.4 | 3.6 | 43.5 | 0.4 |
| Infection | 22.2 | 0 | 16.0 | 1.4 | 13.9 | 0.4 |
| Bilirubin | 87.6 | 7.1 | 92.2 | 8.2 | 83.9 | 7.2 |
| Exfoliative dermatitis | 0.9 | 0 | 3.2 | 0.5 | 0 | 0 |
| Rash | 19.1 | 0 | 26.5 | 0.9 | 14.3 | 0.4 |
| Alopecia Complete hair loss = Grade 2 | 43.1 | -- | 26.5 | -- | 46.1 | -- |
| Dyspnea | 27.6 | 6.3 | 16.0 | 0.5 | 22.0 | 2.2 |
| Cough | 26.7 | 1.3 | 18.3 | 0 | 20.2 | 0.4 |
| Pneumonia | 6.2 | 2.7 | 1.4 | 1.0 | 3.6 | 1.3 |
| Dizziness | 23.1 | 1.3 | 16.4 | 0 | 21.1 | 1.8 |
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, continuedCommon adverse reactions (≥30%) observed in combination therapy clinical studies are: nausea, vomiting, abdominal pain, diarrhea, constipation, anorexia, mucositis, neutropenia, leukopenia (including lymphocytopenia), anemia, thrombocytopenia, asthenia, pain, fever, infection, abnormal bilirubin, alopecia. ( 6.1 ) Common adverse reactions (≥30%) observed in single agent therapy clinical studies are: nausea, vomiting, abdominal pain, diarrhea, constipation, anorexia, neutropenia, leukopenia (including lymphocytopenia), anemia, asthenia, fever, body weight decreasing, alopecia. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Pfizer Inc, at 1-800-438-1985 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Studies 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 clinical practice. Common adverse reactions (≥30%) observed in combination therapy clinical studies are: nausea, vomiting, abdominal pain, diarrhea, constipation, anorexia, mucositis, neutropenia, leukopenia (including lymphocytopenia), anemia, thrombocytopenia, asthenia, pain, fever, infection, abnormal bilirubin, and alopecia.
Source: FDA drug label, NDA020571 (Pfizer Inc), as published by Pharmacia & Upjohn Company LLC, effective May 12, 2026 (SPL set e518dfc6-7e93-4fee-a66c-51e1ab71c056), via openFDA; the full label on DailyMed
What do FAERS reports show?
12,786 reports list irinotecan among the medicines taken, each a report of something that happened, not proof the medicine caused it; 2,639 are coded as a death and 5,216 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, 11 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?
- Irinotecan: 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