Drug interactions
Diltiazem + Methadone
Severity: Moderate
Diltiazem and Methadone: 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
Diltiazem inhibits CYP3A4 and may raise methadone concentrations, increasing the risk of sedation, respiratory depression and QT prolongation. Diltiazem itself can slow heart rate and conduction.
What this interaction means in plain words
Diltiazem and Methadone 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.
Diltiazem belongs to Cardiovascular; Methadone belongs to Musculoskeletal.
Why it happens
Diltiazem inhibits CYP3A4-mediated N-demethylation of methadone, decreasing its clearance.
What to do
Monitor for sedation, respiratory depression and bradycardia when starting or increasing diltiazem, and consider lowering the methadone dose. Obtain an ECG if other QT risk factors exist.
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 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 Diltiazem
- Diltiazem + Flibanserin Contraindicated
- Diltiazem + Ivabradine Contraindicated
- Diltiazem + Lomitapide Contraindicated
- Diltiazem + Lonafarnib Contraindicated
- Acebutolol + Diltiazem Major
- Alfentanil + Diltiazem Major
Frequently asked questions
Can I take Diltiazem with Methadone?
MediHelp rates the interaction as moderate. Diltiazem and Methadone 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. Diltiazem inhibits CYP3A4 and may raise methadone concentrations, increasing the risk of sedation, respiratory depression and QT prolongation. Diltiazem itself can slow heart rate and conduction.
How serious is the interaction between Diltiazem and Methadone?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor for sedation, respiratory depression and bradycardia when starting or increasing diltiazem, and consider lowering the methadone dose. Obtain an ECG if other QT risk factors exist.
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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