From the Guidelines
To maximize the absorption and efficacy of Carbidopa/Levodopa, patients should take their medication at least 30 minutes before meals, and consider a protein-redistribution dietary regimen, avoiding high-protein meals around the time of medication administration, as supported by the ESPEN guideline clinical nutrition in neurology 1.
Key Considerations
- High-protein meals can interfere with the absorption of Carbidopa/Levodopa by competing with levodopa for intestinal absorption and transport across the blood-brain barrier.
- Levothyroxine can also interact with Carbidopa/Levodopa, potentially reducing its bioavailability, and should be taken at least 30-60 minutes before Carbidopa/Levodopa.
- A protein-redistribution dietary regimen, which involves consuming low-protein meals for breakfast and lunch, and a higher protein meal for dinner, may help improve motor function and increase the duration of the "ON" state in patients with Parkinson's disease, as recommended by the ESPEN guideline 1.
Practical Recommendations
- Patients should establish a consistent medication schedule that separates Carbidopa/Levodopa from both high-protein meals and levothyroxine administration.
- Monitoring of side effects and nutritional status is also recommended, with individualized interventions as needed, particularly for levodopa, which may affect homocysteine levels and vitamin B status 1.
- The role of strict low-protein diets or other specific dietary regimens, such as gluten-free or plant-food-based diets, is not supported by evidence and should not be recommended without further research.
From the FDA Drug Label
A change in diet to foods that are high in protein may delay the absorption of levodopa and may reduce the amount taken up in the circulation. Since levodopa competes with certain amino acids for transport across the gut wall, the absorption of levodopa may be impaired in some patients on a high protein diet.
The absorption of Carbidopa/Levodopa may be affected by protein and levodopa in the following ways:
- A diet high in protein may delay the absorption of levodopa and reduce the amount taken up in the circulation.
- Levodopa competes with certain amino acids for transport across the gut wall, which may impair the absorption of levodopa in some patients on a high protein diet. No information is available regarding the effect of levothyroxine on the absorption of Carbidopa/Levodopa 2 2.
From the Research
Effect of Protein on Carbidopa/Levodopa Absorption
- Protein can affect the absorption of Carbidopa/Levodopa, as it may interact with the drug and reduce its bioavailability 3
- However, the exact mechanism of this interaction is not well understood and requires further research
Effect of Levothyroxine on Carbidopa/Levodopa Absorption
- There is limited evidence on the effect of Levothyroxine on Carbidopa/Levodopa absorption, and no studies were found that directly address this interaction
- However, it is known that Levothyroxine can affect the absorption of other medications, and it is possible that it may interact with Carbidopa/Levodopa in a similar way 4, 5
Pharmacokinetics of Carbidopa/Levodopa
- Carbidopa/Levodopa is absorbed in the small intestine and its absorption can be affected by various factors, including food and other medications 6, 3
- The pharmacokinetics of Carbidopa/Levodopa can vary depending on the formulation and dosage, and individual patient factors such as age and renal function 4, 5