Drug interactions
Guanfacine + Metronidazole
Severity: Moderate
Guanfacine and Metronidazole: 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
Metronidazole may increase guanfacine concentrations through CYP3A4 inhibition. This may cause excessive hypotension, bradycardia and sedation.
What this interaction means in plain words
Guanfacine and Metronidazole 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.
Guanfacine belongs to Cardiovascular; Metronidazole belongs to Anti Parasitic.
Why it happens
CYP3A4 inhibition by metronidazole reduces guanfacine metabolism.
What to do
Monitor blood pressure, heart rate and sedation. Consider reducing extended-release guanfacine to half the usual dose per labeling.
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 Metronidazole
- Ethanol + Metronidazole Contraindicated
- Metronidazole + Pimozide Contraindicated
- Amiodarone + Metronidazole Major
- Disulfiram + Metronidazole Major
- Ergotamine + Metronidazole Major
- Lomitapide + Metronidazole 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 Guanfacine with Metronidazole?
MediHelp rates the interaction as moderate. Guanfacine and Metronidazole 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. Metronidazole may increase guanfacine concentrations through CYP3A4 inhibition. This may cause excessive hypotension, bradycardia and sedation.
How serious is the interaction between Guanfacine and Metronidazole?
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 blood pressure, heart rate and sedation. Consider reducing extended-release guanfacine to half the usual dose per labeling.
What other medicines interact with Metronidazole?
MediHelp also lists interactions of Metronidazole with, for example, Ethanol, Pimozide, Amiodarone. The full list is on the Metronidazole page.
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