From the FDA Drug Label
Addition of Other Antiparkinsonian Medications Standard drugs for Parkinson's disease, other than levodopa without a decarboxylase inhibitor, may be used concomitantly while carbidopa and levodopa is being administered, although dosage adjustments may be required The patient is already on Sinemet (carbidopa and levodopa) QID, so adding other antiparkinsonian medications may be considered, but dosage adjustments of the current medication may be required 1.
- The decision to add on therapy should be made on a case-by-case basis, considering the patient's individual response to the current medication and the potential for drug interactions.
- Close monitoring of the patient is necessary to adjust the dosage and minimize potential adverse effects.
From the Research
For a Parkinson's patient already taking Sinemet (carbidopa-levodopa) 50-200mg QID who needs add-on therapy, I recommend adding a dopamine agonist such as pramipexole or a MAO-B inhibitor like selegiline, as these have been shown to be effective in combination with levodopa 2. When considering add-on therapy, it's essential to evaluate the patient's specific symptoms, age, and comorbidities. Dopamine agonists, such as pramipexole (starting at 0.125mg TID and gradually increasing to 0.5-1.5mg TID) or ropinirole (starting at 0.25mg TID and gradually increasing to 1-8mg TID), can be effective in improving motor symptoms. Alternatively, MAO-B inhibitors like selegiline (5mg once or twice daily) or rasagiline (1mg once daily) can also be considered.
- The choice of add-on medication depends on the patient's specific needs and medical history.
- It's crucial to start with low doses and titrate slowly while monitoring for side effects such as nausea, orthostatic hypotension, hallucinations, or impulse control disorders.
- For patients with motor fluctuations, adding entacapone (200mg with each Sinemet dose) can extend levodopa's duration of action, as it prevents peripheral metabolism and increases levodopa brain availability 3.
- A recent study found that selegiline was the best option in combination with levodopa among all the drugs investigated, highlighting its potential as an effective add-on therapy 2.
- Another study suggested that long-term levodopa/dopa decarboxylase inhibitor application with concomitant inhibition of both catechol-O-methyltransferase and monoamine oxidase-B supports a more continuous dopamine substitution, which ameliorates fluctuations of motor behavior 4.