Drug interactions
Hydralazine + Phenylephrine
Severity: Moderate
Hydralazine 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
Phenylephrine raises blood pressure by vasoconstriction and can blunt the blood pressure lowering effect of hydralazine. Hydralazine-induced reflex tachycardia may also be partly opposed.
What this interaction means in plain words
Hydralazine 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.
Hydralazine belongs to Cardiovascular; Phenylephrine belongs to Respiratory.
Why it happens
Pharmacodynamic antagonism between alpha-1 mediated vasoconstriction and direct arteriolar vasodilation.
What to do
Monitor blood pressure when systemic phenylephrine is used in patients treated with hydralazine. Adjust antihypertensive doses if control is lost.
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 Hydralazine
- Amifostine + Hydralazine Major
- Aceclofenac + Hydralazine Moderate
- Acemetacin + Hydralazine Moderate
- Aldesleukin + Hydralazine Moderate
- Avanafil + Hydralazine Moderate
- Benzphetamine + Hydralazine Moderate
Frequently asked questions
Can I take Hydralazine with Phenylephrine?
MediHelp rates the interaction as moderate. Hydralazine 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. Phenylephrine raises blood pressure by vasoconstriction and can blunt the blood pressure lowering effect of hydralazine. Hydralazine-induced reflex tachycardia may also be partly opposed.
How serious is the interaction between Hydralazine 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 when systemic phenylephrine is used in patients treated with hydralazine. Adjust antihypertensive doses if control is lost.
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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