Drug interactions
Clozapine + Guanfacine
Severity: Moderate
Clozapine 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
Both agents lower blood pressure, and clozapine causes orthostatic hypotension and sedation. Together they may lead to marked hypotension, dizziness, syncope and excess sedation.
What this interaction means in plain words
Clozapine 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.
Clozapine belongs to Central Nervous System; Guanfacine belongs to Cardiovascular.
Why it happens
Additive hypotensive and sedative effects: alpha-1 and other receptor blockade from clozapine plus central alpha-2 agonism from guanfacine.
What to do
Monitor blood pressure and heart rate, especially during initiation and dose changes. Counsel patients to rise slowly and reduce the guanfacine dose if symptomatic hypotension occurs.
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 Clozapine
- Clozapine + Deferiprone Contraindicated
- Clozapine + Irinotecan Contraindicated
- Clozapine + Pimozide Contraindicated
- Clozapine + Thioridazine Contraindicated
- Acalabrutinib + Clozapine Major
- Adagrasib + Clozapine 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 Clozapine with Guanfacine?
MediHelp rates the interaction as moderate. Clozapine 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. Both agents lower blood pressure, and clozapine causes orthostatic hypotension and sedation. Together they may lead to marked hypotension, dizziness, syncope and excess sedation.
How serious is the interaction between Clozapine 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: Monitor blood pressure and heart rate, especially during initiation and dose changes. Counsel patients to rise slowly and reduce the guanfacine dose if symptomatic hypotension occurs.
What other medicines interact with Clozapine?
MediHelp also lists interactions of Clozapine with, for example, Deferiprone, Irinotecan, Pimozide. The full list is on the Clozapine page.
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