Drug interactions
Carbidopa-levodopa + Promethazine
Severity: Moderate
Carbidopa-levodopa and Promethazine: 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
Promethazine has dopamine-blocking activity that may worsen parkinsonism and diminish levodopa effect, and it adds sedation.
What this interaction means in plain words
Carbidopa-levodopa and Promethazine 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.
Carbidopa-levodopa belongs to Central Nervous System; Promethazine belongs to Respiratory.
Why it happens
Pharmacodynamic antagonism from D2 receptor blockade by promethazine, with additive sedation.
What to do
Prefer ondansetron or domperidone for nausea, and an alternative antihistamine for allergy. Monitor motor function and sedation if used.
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
Other interactions of Promethazine
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
- Amiodarone + Promethazine Major
- Amisulpride + Promethazine Major
Frequently asked questions
Can I take Carbidopa-levodopa with Promethazine?
MediHelp rates the interaction as moderate. Carbidopa-levodopa and Promethazine 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. Promethazine has dopamine-blocking activity that may worsen parkinsonism and diminish levodopa effect, and it adds sedation.
How serious is the interaction between Carbidopa-levodopa and Promethazine?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Prefer ondansetron or domperidone for nausea, and an alternative antihistamine for allergy. Monitor motor function and sedation if used.
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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