Drug interactions
Metyrosine + Promethazine
Severity: Moderate
Metyrosine 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
Metyrosine depletes catecholamines and can itself cause sedation and extrapyramidal symptoms. Promethazine, a phenothiazine with dopamine-blocking activity, may add to these effects, increasing the risk of parkinsonism, dystonia and drowsiness.
What this interaction means in plain words
Metyrosine 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.
Metyrosine belongs to Miscellaneous; Promethazine belongs to Respiratory.
Why it happens
Additive central dopamine antagonism (promethazine) and catecholamine synthesis inhibition (metyrosine) producing pharmacodynamic synergism.
What to do
Monitor for extrapyramidal symptoms and excess sedation, and consider a non-phenothiazine antiemetic or antihistamine if symptoms appear. Reduce the dose of one agent if movement disorders develop.
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
- Cabergoline + Promethazine Contraindicated
- Dopamine + Promethazine Contraindicated
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
Other interactions of Metyrosine
- Carbidopa-levodopa + Metyrosine Major
- Fluphenazine + Metyrosine Major
- Metoclopramide + Metyrosine Major
- Carbidopa-entacapone-levodopa + Metyrosine Moderate
- Chlorpromazine + Metyrosine Moderate
- Clonidine + Metyrosine Moderate
Frequently asked questions
Can I take Metyrosine with Promethazine?
MediHelp rates the interaction as moderate. Metyrosine 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. Metyrosine depletes catecholamines and can itself cause sedation and extrapyramidal symptoms. Promethazine, a phenothiazine with dopamine-blocking activity, may add to these effects, increasing the risk of parkinsonism, dystonia and drowsiness.
How serious is the interaction between Metyrosine 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: Monitor for extrapyramidal symptoms and excess sedation, and consider a non-phenothiazine antiemetic or antihistamine if symptoms appear. Reduce the dose of one agent if movement disorders develop.
What other medicines interact with Promethazine?
MediHelp also lists interactions of Promethazine with, for example, Cabergoline, Dopamine, Ibutilide. The full list is on the Promethazine page.
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