Drug interactions
Cimetidine + Lapatinib
Severity: Moderate
Cimetidine and Lapatinib: moderate interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Lapatinib absorption depends on an acidic gastric environment, and cimetidine raises gastric pH. Exposure to lapatinib may fall, which could reduce its antitumor effect.
What this interaction means in plain words
Cimetidine and Lapatinib can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Cimetidine belongs to Gastrointestinal Tract; Lapatinib belongs to Oncology.
Why it happens
Reduced gastric acidity decreases the solubility and absorption of oral lapatinib.
What to do
Avoid routine use of H2 blockers with lapatinib where possible; if acid suppression is needed, consider an antacid taken at least several hours before or after lapatinib. Monitor for loss of tumor response.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Cimetidine
- Cimetidine + Dofetilide Contraindicated
- Cimetidine + Fezolinetant Contraindicated
- Alfentanil + Cimetidine Major
- Atazanavir + Cimetidine Major
- Carmustine + Cimetidine Major
- Cimetidine + Citalopram Major
Other interactions of Lapatinib
- Dofetilide + Lapatinib Contraindicated
- Ibutilide + Lapatinib Contraindicated
- Lapatinib + Pimozide Contraindicated
- Lapatinib + Saquinavir Contraindicated
- Lapatinib + Thioridazine Contraindicated
- Adagrasib + Lapatinib Major
Frequently asked questions
Can I take Cimetidine with Lapatinib?
MediHelp rates the interaction as moderate. Cimetidine and Lapatinib can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Lapatinib absorption depends on an acidic gastric environment, and cimetidine raises gastric pH. Exposure to lapatinib may fall, which could reduce its antitumor effect.
How serious is the interaction between Cimetidine and Lapatinib?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid routine use of H2 blockers with lapatinib where possible; if acid suppression is needed, consider an antacid taken at least several hours before or after lapatinib. Monitor for loss of tumor response.
What other medicines interact with Cimetidine?
MediHelp also lists interactions of Cimetidine with, for example, Dofetilide, Fezolinetant, Alfentanil. The full list is on the Cimetidine page.
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