Drug interactions
Carbidopa-levodopa + Olanzapine / samidorphan
Severity: Moderate
Carbidopa-levodopa and Olanzapine / samidorphan: 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
Olanzapine is a dopamine antagonist and may counteract the antiparkinsonian effect of levodopa, potentially worsening motor symptoms. Levodopa in turn may reduce the antipsychotic effect of olanzapine. Olanzapine has less motor liability than older antipsychotics but the opposition is still relevant.
What this interaction means in plain words
Carbidopa-levodopa and Olanzapine / samidorphan 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
Pharmacodynamic antagonism between olanzapine D2 receptor blockade and levodopa-derived dopamine.
What to do
Monitor motor symptoms and psychiatric status, and adjust doses as needed. In Parkinson disease with psychosis, prefer quetiapine or clozapine.
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 Olanzapine / samidorphan?
MediHelp rates the interaction as moderate. Carbidopa-levodopa and Olanzapine / samidorphan 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. Olanzapine is a dopamine antagonist and may counteract the antiparkinsonian effect of levodopa, potentially worsening motor symptoms. Levodopa in turn may reduce the antipsychotic effect of olanzapine. Olanzapine has less motor liability than older antipsychotics but the opposition is still relevant.
How serious is the interaction between Carbidopa-levodopa and Olanzapine / samidorphan?
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 motor symptoms and psychiatric status, and adjust doses as needed. In Parkinson disease with psychosis, prefer quetiapine or clozapine.
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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