From the FDA Drug Label
The incidence of levodopa-induced nausea and vomiting is less with carbidopa and levodopa than with levodopa. In many patients, this reduction in nausea and vomiting will permit more rapid dosage titration. When levodopa is administered orally, it is rapidly decarboxylated to dopamine in extracerebral tissues so that only a small portion of a given dose is transported unchanged to the central nervous system For this reason, large doses of levodopa are required for adequate therapeutic effect, and these may often be accompanied by nausea and other adverse reactions, some of which are attributable to dopamine formed in extracerebral tissues
Nausea associated with Parkinson's disease management, particularly with levodopa therapy, can be mitigated by co-administering carbidopa. The combination of carbidopa and levodopa reduces the incidence of nausea and vomiting compared to levodopa alone, allowing for more rapid dosage titration in many patients 1 2. Key points to consider:
- Carbidopa inhibits decarboxylation of peripheral levodopa, making more levodopa available for transport to the brain.
- The combination of carbidopa and levodopa increases the plasma half-life of levodopa and decreases plasma and urinary dopamine and homovanillic acid.
- Nausea is a common adverse reaction associated with levodopa therapy, particularly when administered in large doses.
From the Research
Nausea in Parkinson's disease is best managed through medication adjustments and specific anti-nausea treatments, with domperidone being the preferred option due to its minimal risk of worsening Parkinson's symptoms. The management of nausea in Parkinson's disease involves a multifaceted approach, including adjusting Parkinson's medications, using anti-nausea medications, and implementing non-pharmacological strategies.
Medication Adjustments
Adjusting Parkinson's medications is essential since dopaminergic drugs like levodopa and dopamine agonists often cause nausea, especially when starting treatment. Taking medications with food (except levodopa, which should be taken 30-60 minutes before meals), starting with low doses and gradually increasing, or using extended-release formulations can help reduce nausea 3.
Anti-Nausea Treatments
For direct nausea treatment, domperidone (10-20mg three times daily) is preferred as it doesn't cross the blood-brain barrier and won't worsen Parkinson's symptoms 4. Ondansetron (4-8mg every 8 hours) is another option. Traditional anti-nausea medications like metoclopramide, prochlorperazine, and promethazine should be avoided as they block dopamine receptors and can worsen Parkinson's symptoms.
Non-Pharmacological Approaches
Non-pharmacological approaches include eating smaller, more frequent meals, staying hydrated, avoiding trigger foods, and using ginger supplements (250-500mg capsules). These strategies work because they either address the peripheral dopamine stimulation causing nausea or provide symptomatic relief without interfering with the central dopaminergic pathways needed to control Parkinson's motor symptoms.
Importance of Adherence
Adherence to pharmacotherapy plays a key role in managing Parkinson's disease symptoms, including nausea, and should be optimized through tailored medication regimens, use of dosing devices or alarms, and good communication with patients and their caregivers 5.
Key Considerations
When managing nausea in Parkinson's disease, it's crucial to consider the potential cardiotoxic effects of domperidone, especially in doses above 30 mg/daily, and to use it with caution, particularly in patients over 60 years old 4. The goal is to balance the management of nausea with the need to control Parkinson's motor symptoms effectively, prioritizing the patient's quality of life and minimizing morbidity and mortality.