From the FDA Drug Label
Drug Interactions Caution should be exercised when the following drugs are administered concomitantly with Carbidopa and levodopa tablets. Dopamine D 2receptor antagonists (e. g., phenothiazines, butyrophenones, risperidone) and isoniazid may reduce the therapeutic effects of levodopa. L-dopa: Coadministration of carbidopa + L-dopa (10/100 mg twice daily) with ropinirole (2 mg 3 times daily) had no effect on the steady-state pharmacokinetics of ropinirole (n = 28 patients)
The interaction between Sinemet (Carbidopa/Levodopa) and Olanzapine (an atypical antipsychotic and dopamine D2 receptor antagonist) may reduce the therapeutic effects of levodopa. The interaction between Sinemet (Carbidopa/Levodopa) and Ropinirole is not expected to affect the pharmacokinetics of ropinirole, but ropinirole may increase the mean steady-state Cmax of L-dopa by 20%. 1 2
From the Research
Sinemet (carbidopa-levodopa), olanzapine, and ropinirole should not be taken together without careful medical supervision due to potential drug interactions.
Potential Interactions and Considerations
- Sinemet and ropinirole are both used to treat Parkinson's disease but work through different mechanisms - Sinemet increases dopamine levels while ropinirole directly stimulates dopamine receptors.
- Using them together may be appropriate in advanced Parkinson's disease but requires dose adjustments to prevent excessive dopaminergic effects.
- Olanzapine, an antipsychotic medication, can worsen Parkinson's symptoms by blocking dopamine receptors, potentially counteracting the benefits of Sinemet and ropinirole.
- This combination may be prescribed in specific situations, such as when a patient with Parkinson's disease develops psychosis, but requires careful monitoring for worsening motor symptoms, sedation, and other side effects.
- Dosing must be individualized based on symptom control and side effect profile, as supported by studies such as 3 which compared the effectiveness of dopamine agonists and monoamine oxidase type-B inhibitors for Parkinson's disease.
Monitoring and Coordination of Care
- If you're currently taking these medications or considering this combination, consult your neurologist and psychiatrist to ensure proper coordination of care and monitoring for potential adverse effects.
- Regular monitoring for motor symptoms, sedation, and other side effects is crucial when taking this combination, as noted in studies like 4 which discussed the management of Parkinson's disease with COMT inhibitors.
- The most recent study 5 on opicapone, a new COMT inhibitor, highlights the importance of careful dosing and monitoring in the treatment of Parkinson's disease, which can be applied to the combination of Sinemet, olanzapine, and ropinirole.