Drug interactions
Clozapine + Phenylephrine
Severity: Moderate
Clozapine and Phenylephrine: 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
Clozapine blocks alpha-1 receptors and commonly causes orthostatic hypotension, which can reduce the pressor response to phenylephrine. Higher vasopressor doses may be needed in clozapine-treated patients with hypotension.
What this interaction means in plain words
Clozapine and Phenylephrine 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; Phenylephrine belongs to Respiratory.
Why it happens
Alpha-1 adrenergic antagonism by clozapine opposes phenylephrine's vasoconstrictor action.
What to do
Monitor blood pressure and titrate phenylephrine to response. Avoid using epinephrine for clozapine-related hypotension.
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 Phenylephrine
- Isocarboxazid + Phenylephrine Contraindicated
- Phenelzine + Phenylephrine Contraindicated
- Phenylephrine + Tranylcypromine Contraindicated
- Bromocriptine + Phenylephrine Major
- Cocaine + Phenylephrine Major
- Dihydroergotamine intranasal + Phenylephrine Major
Other interactions of Clozapine
- Clozapine + Deferiprone Contraindicated
- Clozapine + Irinotecan Contraindicated
- Clozapine + Pimozide Contraindicated
- Clozapine + Thioridazine Contraindicated
- Acalabrutinib + Clozapine Major
- Adagrasib + Clozapine Major
Frequently asked questions
Can I take Clozapine with Phenylephrine?
MediHelp rates the interaction as moderate. Clozapine and Phenylephrine 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 blocks alpha-1 receptors and commonly causes orthostatic hypotension, which can reduce the pressor response to phenylephrine. Higher vasopressor doses may be needed in clozapine-treated patients with hypotension.
How serious is the interaction between Clozapine and Phenylephrine?
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 titrate phenylephrine to response. Avoid using epinephrine for clozapine-related hypotension.
What other medicines interact with Phenylephrine?
MediHelp also lists interactions of Phenylephrine with, for example, Isocarboxazid, Phenelzine, Tranylcypromine. The full list is on the Phenylephrine page.
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