What the label lists and what reports show
Neratinib side effects
Neratinib's FDA label: “The most common adverse reactions (reported in ≥5% of patients) were: NERLYNX as a single agent: diarrhea, nausea, abdominal pain, fatigue, vomiting, rash, stomatitis, decreased appetite, muscle spasms, dyspepsia, AST or ALT increased, nail disorder, dry …” FAERS holds 2,294 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 (1,249 reports).
- No generic listed
Check it at the source: the neratinib FDA label on DailyMed (effective July 2, 2026, Puma Biotechnology, Inc.); 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 NERLYNX?NERLYNX may cause serious side effects, including: See " What is the most important information I should know about NERLYNX? " Liver problems. Changes in liver function tests are common with NERLYNX. Your healthcare provider should do blood tests before you begin treatment, monthly during the first 3 months, and then every 3 months as needed during treatment with NERLYNX. Your healthcare provider will stop your treatment with NERLYNX if your liver tests show severe problems. […]
Source: FDA drug label, Puma Biotechnology, Inc., effective July 2, 2026 (SPL set d1e41dcf-e82a-47c2-a0ad-6c6eef621834), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsThe most common adverse reactions (reported in ≥5% of patients) were: NERLYNX as a single agent: diarrhea, nausea, abdominal pain, fatigue, vomiting, rash, stomatitis, decreased appetite, muscle spasms, dyspepsia, AST or ALT increased, nail disorder, dry skin, abdominal distention, epistaxis, weight decreased, and urinary tract infection.
Table 7: Adverse Reactions Reported in ≥2% of NERLYNX-Treated Patients in ExteNET
| Reaction | All Grades (%) | Grade 3 (%) | Grade 4 (%) | All Grades (%) | Grade 3 (%) | Grade 4 (%) |
|---|---|---|---|---|---|---|
| Diarrhea | 95 | 40 | 0.1 | 35 | 2 | 0 |
| Nausea | 43 | 2 | 0 | 22 | 0.1 | 0 |
| Abdominal pain | 36 | 2 | 0 | 15 | 0.4 | 0 |
| Vomiting | 26 | 3 | 0 | 8 | 0.4 | 0 |
| Stomatitis | 14 | 0.6 | 0 | 6 | 0.1 | 0 |
| Dyspepsia | 10 | 0.4 | 0 | 4 | 0 | 0 |
| Abdominal distension | 5 | 0.3 | 0 | 3 | 0 | 0 |
| Dry mouth | 3 | 0.1 | 0 | 2 | 0 | 0 |
| Fatigue | 27 | 2 | 0 | 20 | 0.4 | 0 |
| Alanine aminotransferase increased | 9 | 1 | 0.2 | 3 | 0.2 | 0 |
| Aspartate aminotransferase increased | 7 | 0.5 | 0.2 | 3 | 0.3 | 0 |
| Urinary tract infection | 5 | 0.1 | 0 | 2 | 0 | 0 |
| Weight decreased | 5 | 0.1 | 0 | 0.5 | 0 | 0 |
| Decreased appetite | 12 | 0.2 | 0 | 3 | 0 | 0 |
| Dehydration | 4 | 0.9 | 0.1 | 0.4 | 0.1 | 0 |
| Muscle spasms | 11 | 0.1 | 0 | 3 | 0.1 | 0 |
| Epistaxis | 5 | 0 | 0 | 1 | 0.1 | 0 |
| Rash | 18 | 0.6 | 0 | 9 | 0 | 0 |
| Dry skin | 6 | 0 | 0 | 2 | 0 | 0 |
| Nail disorder | 8 | 0.3 | 0 | 2 | 0 | 0 |
| Skin fissures | 2 | 0.1 | 0 | 0.1 | 0 | 0 |
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: Diarrhea [see Warnings and Precautions ( 5.1 )] Hepatotoxicity [see Warnings and Precautions ( 5.2 )] The most common adverse reactions (reported in ≥5% of patients) were: NERLYNX as a single agent: diarrhea, nausea, abdominal pain, fatigue, vomiting, rash, stomatitis, decreased appetite, muscle spasms, dyspepsia, AST or ALT increased, nail disorder, dry skin, abdominal distention, epistaxis, weight decreased, and urinary tract infection. ( 6 ) NERLYNX in combination with capecitabine: diarrhea, nausea, vomiting, decreased appetite, constipation, fatigue/asthenia, weight decreased, dizziness, back pain, arthralgia, urinary tract infection, upper respiratory tract infection, abdominal distention, renal impairment, and muscle spasms. ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Puma Biotechnology, Inc. at 1-844-NERLYNX (1-844-637-5969) 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, Puma Biotechnology, Inc., effective July 2, 2026 (SPL set d1e41dcf-e82a-47c2-a0ad-6c6eef621834), via openFDA; the full label on DailyMed
What do FAERS reports show?
2,294 reports list neratinib among the medicines taken, each a report of something that happened, not proof the medicine caused it; 360 are coded as a death and 678 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, 15 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?
- Neratinib: 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