Drug interactions
Levodopa + Promethazine
Severity: Moderate
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 is a phenothiazine with dopamine D2 receptor blocking activity. This opposes the dopaminergic effect of levodopa and may worsen parkinsonian symptoms such as rigidity and bradykinesia.
What this interaction means in plain words
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.
Levodopa belongs to Central Nervous System; Promethazine belongs to Respiratory.
Why it happens
Pharmacodynamic antagonism, with central dopamine D2 receptor blockade by promethazine opposing levodopa-derived dopamine.
What to do
Avoid promethazine in Parkinson's disease where possible and use an alternative such as domperidone (where available) or ondansetron for nausea. Monitor motor function if it must be 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 Promethazine
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
- Amiodarone + Promethazine Major
- Amisulpride + Promethazine Major
Other interactions of Levodopa
- Isocarboxazid + Levodopa Contraindicated
- Levodopa + Phenelzine Contraindicated
- Levodopa + Phenelzine (nonselective MAOI) Contraindicated
- Levodopa + Procarbazine Contraindicated
- Levodopa + Tranylcypromine Contraindicated
- Amisulpride + Levodopa Major
Frequently asked questions
Can I take Levodopa with Promethazine?
MediHelp rates the interaction as moderate. 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 is a phenothiazine with dopamine D2 receptor blocking activity. This opposes the dopaminergic effect of levodopa and may worsen parkinsonian symptoms such as rigidity and bradykinesia.
How serious is the interaction between 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: Avoid promethazine in Parkinson's disease where possible and use an alternative such as domperidone (where available) or ondansetron for nausea. Monitor motor function if it must be used.
What other medicines interact with Promethazine?
MediHelp also lists interactions of Promethazine with, for example, Ibutilide, Pimozide, Thioridazine. The full list is on the Promethazine page.
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