Drug interactions
Diltiazem + Guanfacine
Severity: Moderate
Diltiazem and Guanfacine: 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 raises guanfacine levels, which may cause hypotension, bradycardia and sedation. Both agents also lower heart rate and blood pressure.
What this interaction means in plain words
Diltiazem and Guanfacine 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; Guanfacine belongs to Cardiovascular.
Why it happens
Diltiazem inhibits CYP3A4 metabolism of guanfacine, with additive hemodynamic effects.
What to do
Halve the guanfacine ER dose when starting with diltiazem and monitor blood pressure and heart rate. Increase the dose again if diltiazem is stopped.
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 Diltiazem
- Diltiazem + Flibanserin Contraindicated
- Diltiazem + Ivabradine Contraindicated
- Diltiazem + Lomitapide Contraindicated
- Diltiazem + Lonafarnib Contraindicated
- Acebutolol + Diltiazem Major
- Alfentanil + Diltiazem Major
Other interactions of Guanfacine
- Clonidine + Guanfacine Major
- Guanfacine + Lofexidine Major
- Aldesleukin + Guanfacine Moderate
- Amiodarone + Guanfacine Moderate
- Amisulpride + Guanfacine Moderate
- Amitriptyline + Guanfacine Moderate
Frequently asked questions
Can I take Diltiazem with Guanfacine?
MediHelp rates the interaction as moderate. Diltiazem and Guanfacine 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 raises guanfacine levels, which may cause hypotension, bradycardia and sedation. Both agents also lower heart rate and blood pressure.
How serious is the interaction between Diltiazem and Guanfacine?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Halve the guanfacine ER dose when starting with diltiazem and monitor blood pressure and heart rate. Increase the dose again if diltiazem is stopped.
What other medicines interact with Diltiazem?
MediHelp also lists interactions of Diltiazem with, for example, Flibanserin, Ivabradine, Lomitapide. The full list is on the Diltiazem page.
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