Drug interactions
Lapatinib + Methadone
Severity: Major
Lapatinib and Methadone: major 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
Both drugs can prolong the QT interval, and lapatinib inhibits CYP3A4, which may raise methadone levels. Together these increase the risk of torsades de pointes and opioid toxicity.
What this interaction means in plain words
Lapatinib and Methadone can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Lapatinib belongs to Oncology; Methadone belongs to Musculoskeletal.
Why it happens
Additive QTc prolongation plus CYP3A4 inhibition by lapatinib reducing methadone clearance.
What to do
Check a baseline ECG and monitor QTc, and correct potassium and magnesium. Watch for sedation and respiratory depression and reduce the methadone dose if needed.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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Other interactions of Methadone
- Alvimopan + Methadone Contraindicated
- Calcium / magnesium / potassium / sodium oxybates + Methadone Contraindicated
- Droperidol + Methadone Contraindicated
- Ibutilide + Methadone Contraindicated
- Isocarboxazid + Methadone Contraindicated
- Lefamulin + Methadone Contraindicated
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 Lapatinib with Methadone?
MediHelp rates the interaction as major. Lapatinib and Methadone can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Both drugs can prolong the QT interval, and lapatinib inhibits CYP3A4, which may raise methadone levels. Together these increase the risk of torsades de pointes and opioid toxicity.
How serious is the interaction between Lapatinib and Methadone?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Check a baseline ECG and monitor QTc, and correct potassium and magnesium. Watch for sedation and respiratory depression and reduce the methadone dose if needed.
What other medicines interact with Methadone?
MediHelp also lists interactions of Methadone with, for example, Alvimopan, Calcium / magnesium / potassium / sodium oxybates, Droperidol. The full list is on the Methadone page.
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