What the label lists and what reports show
Lapatinib ditosylate side effects
Lapatinib ditosylate's FDA label: “The most common (greater than 20%) adverse reactions during treatment with lapatinib plus capecitabine were diarrhea, palmar-plantar erythrodysesthesia, nausea, rash, vomiting, and fatigue.” FAERS holds 15,427 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 (4,173 reports).
- Generic listed
- Boxed warning
Check it at the source: the lapatinib ditosylate FDA label on DailyMed (effective November 30, 2023, Teva Pharmaceuticals, 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 lapatinib tablets ?Lapatinib tablets may cause serious side effects, including: heart problems, including decreased pumping of blood from the heart and an abnormal heartbeat. Signs and symptoms of an abnormal heartbeat include: feeling like your heart is pounding or racing dizziness tiredness feeling lightheaded shortness of breath Your healthcare provider should check your heart function before you start taking lapatinib tablets and during treatment. liver problems. Liver problems can be severe and deaths have happened. Signs and symptoms of liver problems include: itching yellowing of your skin or the white part of your eyes dark urine pain or discomfort in the right upper stomach area Your healthcare provider should do blood tests to check your liver before you start taking lapatinib tablets and during treatment. diarrhea. Diarrhea is common with lapatinib tablets and may sometimes be severe. […]
Source: FDA drug label, Teva Pharmaceuticals, Inc., effective November 30, 2023 (SPL set b09abf73-1eef-4e12-b400-c030d546d223), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsThe most common (greater than 20%) adverse reactions during treatment with lapatinib plus capecitabine were diarrhea, palmar-plantar erythrodysesthesia, nausea, rash, vomiting, and fatigue.
Table 5. Adverse Reactions Occurring in Greater Than or Equal to 10% of Patients
| Reactions | All Grades a (%) | Grade 3 (%) | Grade 4 (%) | All Grades a (%) | Grade 3 (%) | Grade 4 (%) | All Grades a (%) | Grade 3 (%) | Grade 4 (%) |
|---|---|---|---|---|---|---|---|---|---|
| Diarrhea | 69 | 13 | 0 | 51 | 6 | 0 | 9 | 0 | 0 |
| Nausea | 22 | 0 | 0 | 22 | 2 | 0 | 9 | 0 | 0 |
| Stomatitis | 17 | 0 | 0 | 13 | < 1 | 0 | 3 | 0 | 0 |
| Vomiting | 10 | 0 | 0 | 14 | 0 | 0 | < 1 | < 1 | 0 |
| Rash b | 54 | 0 | 0 | 44 | 3 | 0 | 5 | 0 | 0 |
| Palmar-plantar erythrodysesthesia | 10 | 0 | 0 | 8 | < 1 | 0 | < 1 | 0 | 0 |
| Alopecia | 10 | 0 | 0 | 7 | 0 | 0 | 2 | 0 | 0 |
| Fatigue | 12 | < 1 | 0 | 14 | 2 | 0 | 10 | 0 | 0 |
| Arthralgia | 13 | < 1 | 0 | 14 | 0 | 0 | 12 | 0 | 0 |
| Pain in extremity | 7 | < 1 | 0 | 10 | 0 | 0 | 3 | 0 | 0 |
| Cough | 8 | 0 | 0 | 8 | 0 | 0 | 15 | 0 | 0 |
| Decreased appetite | 18 | 0 | 0 | 13 | 0 | 0 | 3 | 0 | 0 |
| Paronychia | 30 | 0 | 0 | 15 | 2 | 0 | 0 | 0 | 0 |
| Alanine aminotransferase increased | 7 | 0 | 0 | 15 | 3 | < 1 | 6 | 4 | 0 |
| Aspartate aminotransferase increased | 6 | 0 | 0 | 17 | 5 | 0 | 9 | 4 | 0 |
| Headache | 5 | 0 | 0 | 16 | 2 | 0 | 10 | < 1 | 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 most common (greater than 20%) adverse reactions during treatment with lapatinib plus capecitabine were diarrhea, palmar-plantar erythrodysesthesia, nausea, rash, vomiting, and fatigue. The most common (greater than or equal to 20%) adverse reactions during treatment with lapatinib plus letrozole were diarrhea, rash, nausea, and fatigue. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Teva at 1-888-838-2872 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. HER2-Positive Metastatic Breast Cancer: The safety of lapatinib has been evaluated in more than 12,000 patients in clinical trials. The efficacy and safety of lapatinib in combination with capecitabine in breast cancer was evaluated in 198 patients in a randomized, Phase 3 trial [see Clinical Studies ( 14.1 )]. Adverse reactions, which occurred in at least 10% of patients in either treatment arm and were higher in the combination arm, are shown in Table 1. …
Source: FDA drug label, Teva Pharmaceuticals, Inc., effective November 30, 2023 (SPL set b09abf73-1eef-4e12-b400-c030d546d223), via openFDA; the full label on DailyMed
What do FAERS reports show?
15,427 reports list lapatinib ditosylate among the medicines taken, each a report of something that happened, not proof the medicine caused it; 2,475 are coded as a death and 4,010 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 22 reactions below, 13 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?
- Lapatinib ditosylate: 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