Drug interactions
Carbidopa-entacapone-levodopa + Promethazine
Severity: Moderate
Carbidopa-entacapone-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 some dopamine receptor blocking activity and may reduce levodopa benefit or worsen parkinsonism. It also causes sedation and anticholinergic effects, which can add to confusion in older patients.
What this interaction means in plain words
Carbidopa-entacapone-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-entacapone-levodopa belongs to Central Nervous System; Promethazine belongs to Respiratory.
Why it happens
Weak D2 antagonism by a phenothiazine antihistamine opposes dopaminergic therapy.
What to do
Prefer ondansetron or another non-dopamine-blocking agent for nausea. If promethazine is used, monitor motor control and sedation.
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-entacapone-levodopa
- Carbidopa-entacapone-levodopa + Isocarboxazid Contraindicated
- Carbidopa-entacapone-levodopa + Phenelzine Contraindicated
- Carbidopa-entacapone-levodopa + Selegiline transdermal Contraindicated
- Carbidopa-entacapone-levodopa + Tranylcypromine Contraindicated
- Amisulpride + Carbidopa-entacapone-levodopa Major
- Asenapine transdermal + Carbidopa-entacapone-levodopa Major
Other interactions of Promethazine
- Cabergoline + Promethazine Contraindicated
- Dopamine + Promethazine Contraindicated
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
Frequently asked questions
Can I take Carbidopa-entacapone-levodopa with Promethazine?
MediHelp rates the interaction as moderate. Carbidopa-entacapone-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 some dopamine receptor blocking activity and may reduce levodopa benefit or worsen parkinsonism. It also causes sedation and anticholinergic effects, which can add to confusion in older patients.
How serious is the interaction between Carbidopa-entacapone-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 another non-dopamine-blocking agent for nausea. If promethazine is used, monitor motor control and sedation.
What other medicines interact with Carbidopa-entacapone-levodopa?
MediHelp also lists interactions of Carbidopa-entacapone-levodopa with, for example, Isocarboxazid, Phenelzine, Selegiline transdermal. The full list is on the Carbidopa-entacapone-levodopa page.
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