[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [HER2 tyrosine kinase inhibitors](https://durgical.com/en/pharmacology/classes/her2-tyrosine-kinase-inhibitors/) › Lapatinib

# Lapatinib

## HER2 tyrosine kinase inhibitors?

HER2 tyrosine kinase inhibitors

## High alert?

An error with this medicine can cause serious harm: double checks and protocols are used.

## Pregnancy: avoid?

Avoid in pregnancy. Can harm the fetus: a pregnancy test is done before starting, effective contraception is used during treatment and for a time afterwards (by women and by men…

An oral dual HER2 and EGFR kinase inhibitor for HER2-positive breast cancer, with capecitabine or letrozole. Boxed warning: liver damage.

Updated Nov 1, 2026

Also called: lapatinib ditosylate, GW572016

## Quick facts

**Group**
[HER2 tyrosine kinase inhibitors](https://durgical.com/en/pharmacology/classes/her2-tyrosine-kinase-inhibitors/)

**Target**
HER2 (ERBB2) and EGFR tyrosine kinases

**Used for**
HER2-positive advanced · Hormone receptor-positive

**Key effects**
Diarrhoea · Acne-like rash and dry skin · Nausea

**Monitor**
Liver tests before and during treatment

**ATC**
L01EH01

No doses: the clinician sets them by the current guideline.

On this page

- The basics Mechanism of action
- Indications
- Adverse effects
- Pharmacokinetics
- Memory aid

- Clinical What the labels mean

- Safety Contraindications
- Key interactions
- What is monitored
- Administration and safety
- Pregnancy and breastfeeding
- Nursing care

- Study Test yourself

- Connections Connections

## Mechanism of action

✂**HER2 (ERBB2) and EGFR tyrosine kinases**Lapatinib

ⓘ The figure shows lapatinib (GW572016) in the ATP pocket of the human EGFR kinase domain; it binds the matching site of HER2.

**Target in 3D:** HER2 (ERBB2) and EGFR tyrosine kinases. PDB structure 1XKK (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/1XKK) · Drag to rotate · pinch to zoom

Lapatinib reversibly blocks the ATP site of both HER2 and EGFR kinases. In HER2-overexpressing breast cancer this switches off the receptor signal from inside the cell, so it still works in tumours that have become resistant to trastuzumab.

- HER2 overexpression drives breast cancer growth
- Lapatinib blocks the ATP site of HER2 and EGFR
- Works from inside, even after trastuzumab resistance

## Indications

- HER2-positive advanced or metastatic breast cancer previously treated with an anthracycline, a taxane and trastuzumab, with capecitabine. [Breast cancer →](https://durgical.com/en/conditions/breast-cancer/)
- Hormone receptor-positive, HER2-positive metastatic breast cancer in postmenopausal women, with letrozole. [Breast cancer →](https://durgical.com/en/conditions/breast-cancer/)

## Adverse effects

### Common

- Diarrhoea, which can be severe (worse with capecitabine)
- Acne-like rash and dry skin
- Nausea, vomiting, heartburn and reflux
- Red, painful or tingling hands and feet
- Mouth sores, decreased appetite, trouble sleeping

### Serious (rare, important)

- Severe hepatotoxicity (boxed warning), weeks to months after starting
- Reduced left ventricular function
- QT prolongation
- Interstitial lung disease or pneumonitis
- Severe skin reactions

## Contraindications

- Used with caution in heart disease, long QT and low potassium or magnesium

## Key interactions

**Strong CYP3A4 inhibitors (clarithromycin, itraconazole, ketoconazole, ritonavir) and grapefruit**
Raise its levels and its toxicity.

**Strong CYP3A4 inducers (rifampicin, carbamazepine, phenytoin, St John's wort)**
Lower its levels and can make it fail.

**Other QT-prolonging drugs (some antiarrhythmics, macrolides, antipsychotics)**
Additive risk of QT prolongation and arrhythmia.

## What is monitored

- Liver tests before and during treatment
- Heart function (ejection fraction) and ECG
- Potassium and magnesium
- Stool frequency and hydration

## Administration and safety

- Oral tablets once daily, at least an hour away from a meal, swallowed whole.
- Grapefruit, its juice and St John's wort are avoided because they change its levels.

## Pregnancy and breastfeeding

Avoid in pregnancy. Can harm the fetus: a pregnancy test is done before starting, effective contraception is used during treatment and for a time afterwards (by women and by men with partners who could conceive), and breastfeeding is avoided.

## Nursing care

- Check liver tests before refills as ordered; teach to report jaundice, dark urine or itching.
- Teach a diarrhoea plan and the signs of dehydration.
- Report breathlessness, swelling or palpitations.
- Confirm a negative pregnancy test before the first dose and teach contraception during treatment and afterwards.

## Pharmacokinetics

**Absorption**
Oral tablets, once daily, away from meals.

**Metabolism**
Liver, CYP3A4.

**Half-life**
About 14 hours.

## Memory aid

«LAPatinib LAPs two receptors»: HER2 and EGFR, from inside the cell, where trastuzumab cannot reach; the liver pays the price.

## Test yourself

Think of the answer, then tap the question to see it.

## Which two kinases does lapatinib inhibit?

HER2 (ERBB2) and EGFR.

## What is lapatinib's boxed warning?

Severe, possibly fatal hepatotoxicity; liver tests are checked before and during treatment.

## With which oral chemotherapy is lapatinib combined, and which side effect gets worse?

Capecitabine; diarrhoea becomes worse.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/lapatinib/)

[More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology)

## What the labels mean

**High alert**
An error with this medicine can cause serious harm: double checks and protocols are used.

**Pregnancy: avoid**
Avoid in pregnancy. Can harm the fetus: a pregnancy test is done before starting, effective contraception is used during treatment and for a time afterwards (by women and by men…

## Connections

## Related drugs 4

- [Tucatinib](https://durgical.com/en/pharmacology/tucatinib/)
- [Trastuzumab](https://durgical.com/en/pharmacology/trastuzumab/)
- [Capecitabine](https://durgical.com/en/pharmacology/capecitabine/)
- [Letrozole](https://durgical.com/en/pharmacology/letrozole/)

## Related conditions 1

- [Breast cancer](https://durgical.com/en/conditions/breast-cancer/)

[← Back to the class: HER2 tyrosine kinase inhibitors](https://durgical.com/en/pharmacology/classes/her2-tyrosine-kinase-inhibitors/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [Lapatinib: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a607055.html) (MedlinePlus (U.S. National Library of Medicine), 2019); [Lapatinib Ditosylate - NCI](https://www.cancer.gov/about-cancer/treatment/drugs/lapatinibditosylate) (National Cancer Institute, 2024); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=L01EH01) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/pharmacology/lapatinib/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/lapatinib/