Drug interactions
Carbidopa-levodopa + Phenoxybenzamine
Severity: Moderate
Carbidopa-levodopa and Phenoxybenzamine: 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
Phenoxybenzamine is a long-acting alpha-blocker that causes marked vasodilation and orthostatic hypotension. Levodopa also lowers standing blood pressure, so the combination can cause additive hypotension, dizziness and syncope.
What this interaction means in plain words
Carbidopa-levodopa and Phenoxybenzamine 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.
Why it happens
Additive hypotensive effects of irreversible alpha-adrenergic blockade and levodopa-induced orthostatic hypotension.
What to do
Monitor supine and standing blood pressure during initiation and dose changes. Reduce the phenoxybenzamine dose if orthostatic symptoms occur.
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 Carbidopa-levodopa
- Carbidopa-levodopa + Isocarboxazid Contraindicated
- Carbidopa-levodopa + Phenelzine Contraindicated
- Carbidopa-levodopa + Selegiline transdermal Contraindicated
- Carbidopa-levodopa + Tranylcypromine Contraindicated
- Amisulpride + Carbidopa-levodopa Major
- Asenapine + Carbidopa-levodopa Major
Frequently asked questions
Can I take Carbidopa-levodopa with Phenoxybenzamine?
MediHelp rates the interaction as moderate. Carbidopa-levodopa and Phenoxybenzamine 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. Phenoxybenzamine is a long-acting alpha-blocker that causes marked vasodilation and orthostatic hypotension. Levodopa also lowers standing blood pressure, so the combination can cause additive hypotension, dizziness and syncope.
How serious is the interaction between Carbidopa-levodopa and Phenoxybenzamine?
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 supine and standing blood pressure during initiation and dose changes. Reduce the phenoxybenzamine dose if orthostatic symptoms occur.
What other medicines interact with Carbidopa-levodopa?
MediHelp also lists interactions of Carbidopa-levodopa with, for example, Isocarboxazid, Phenelzine, Selegiline transdermal. The full list is on the Carbidopa-levodopa page.
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