Levodopa/carbidopa (drug interactions)
Levodopa/carbidopa is a medication commonly prescribed for the treatment of Parkinson's disease, marketed under the trade name Sinemet. While effective in managing symptoms, it can interact negatively with various substances, potentially reducing its efficacy or causing harmful side effects. Notable interactions include branched-chain amino acids and high-protein foods, which can impair the absorption of the medication, leading to increased symptoms of Parkinson's disease. Additionally, iron supplements can significantly decrease the effectiveness of levodopa/carbidopa, necessitating careful timing when taken.
Other substances, such as the herbal supplement kava, may neutralize the therapeutic effects, while 5-HTP is linked to potentially serious skin conditions when combined with carbidopa. Traditional Chinese herbal remedies and vitamin B6 may also reduce the drug's effectiveness. On the other hand, supplements like SAMe may hold promise for improving certain conditions related to Parkinson's disease, but they could also pose risks of reduced efficacy over time. Patients should be cautious with herbs, supplements, and certain prescription drugs, including antipsychotics and MAO inhibitors, as these can exacerbate symptoms or lead to dangerous side effects. Consultation with a healthcare provider is crucial for anyone using levodopa/carbidopa to manage their treatment plan safely.
Levodopa/carbidopa (drug interactions)
DEFINITION: Levodopa in combination with carbidopa is used in treating Parkinson’s disease.
TRADE NAME: Sinemet
INTERACTIONS: Branched-chain amino acids, 5-HTP (5-hydroxytryptophan), iron, kava, policosanol, SAMe, traditional Chinese herbal medicine, St. John's wort, tyramine, high-protein foods, various prescription medications, vitamin B6
5-HTP (5-hydroxytryptophan)
Effect: Possible Harmful Interaction
The body uses the natural substance 5-HTP to manufacture serotonin, and supplemental forms of 5-HTP have been used for treating depression and migraine headaches. Since the body converts it to serotonin, 5-HTP might have antidepressant properties. For this reason, some people with Parkinson's-related depression have tried it.
However, the combination of 5-HTP and carbidopa might cause a scleroderma-like condition in which the skin becomes hard and tight. Because of the risk of this side effect, persons taking levodopa/carbidopa for Parkinson’s disease should avoid supplemental 5-HTP.
Branched-Chain Amino Acids (BCAAs)
Effect: Possible Harmful Interaction
Branched-chain amino acids (BCAAs) in supplement form have been used to improve appetite in cancer patients and to slow the progression of amyotrophic lateral sclerosis (ALS, or Lou Gehrig’s disease). Dietary protein can decrease the effectiveness of levodopa in Parkinson’s disease. Because the amino acids in proteins affect levodopa, BCAAs might cause the same problem. Therefore, if one takes levodopa/carbidopa for Parkinson’s, it may be advisable to avoid BCAAs and other amino acid supplements. High-protein foods should also be avoided with taking levodopa/carbidopa.
Iron
Effect: Take at a Different Time of Day
Iron appears to interfere with the absorption of both levodopa and carbidopa by binding to them. Studies have found that blood levels of levodopa and carbidopa are reduced 30 to 51 percent and 75 percent, respectively, by iron supplementation, resulting in a worsening of symptoms of Parkinson’s disease. Based on this finding, one should separate the times one takes iron and these drugs by as long as possible.
Kava
Effect: Possible Harmful Interaction
The herb kava (Piper methysticum) has a sedative effect and is used for anxiety and insomnia. A few case reports suggest that kava might interfere with the action of dopamine in the body. This could at least partially neutralize the therapeutic effects of levodopa. In one individual, Parkinson’s disease symptoms got worse following supplementation with kava extract of 150 milligrams (mg) twice daily for ten days. Based on these reports, it may be advisable to avoid kava during levodopa/carbidopa therapy.
Traditional Chinese Herbal Medicine
Effect: Possible Reduced Action of Drug
Certain herbal formulas used in traditional Chinese herbal medicine to treat upset stomach might reduce the effectiveness of levodopa.
Vitamin B6
Effect: Possible Reduced Action of Drug
If taking levodopa alone, one should not take more than 5 mg per day of vitamin B6, or it might impair the drug's effectiveness. However, this issue is not a concern if one uses levodopa/carbidopa combinations that provide a total daily dose of at least 75 mg of carbidopa.
Policosanol
Effect: Possible Benefits and Risks
Policosanol may increase both the beneficial effects and the side effects of levodopa.
SAMe (S-adenosylmethionine)
Effect: Possible Benefits and Risks
SAMe is a naturally occurring compound derived from the amino acid methionine and the energy molecule adenosine triphosphate (ATP). SAMe is widely used as a supplement for treating osteoarthritis and depression. Preliminary evidence suggests that levodopa might deplete levels of SAMe in the body. This suggests (but definitely does not prove) that persons taking levodopa/carbidopa might benefit from SAMe supplements.
One short-term (thirty-day) double-blind study suggests that such combination treatment is safe and might help depression related to Parkinson’s disease. However, there are also concerns that SAMe could cause levodopa to be less effective over time. Persons taking levodopa/carbidopa should consult their physician about taking SAMe.
Other Interactions
Several other interactions exist between levodopa/carbidopa and other herbs, supplements, and prescription medications. St. John's wort can decrease the drug combination's effectiveness, and Parkinson's symptoms could worsen. Foods rich in tyramine can cause a dangerous side effect called cranial hypertension when combined with levodopa/carbidopa. This is characterized by increased swelling and pressure in the skull. Patients are advised not to take monoamine oxidase (MAO) inhibitors when taking levodopa/carbidopa, as this can cause a dangerous rise in blood pressure. Antipsychotic drugs may interfere with levodopa/carbidopa effectiveness. Finally, anticholinergics, antihypertensives, and benzodiazepines should be avoided as well.
Bibliography
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Cimons, Marlene. "Certain Foods and Beverages Can Interact with Drugs." Washington Post, 5 Dec. 2021, www.washingtonpost.com/health/drug-interactions-food-drinks/2021/12/03/348e8048-47c6-11ec-95dc-5f2a96e00fa3‗story.html. Accessed 3 Jan. 2022.
Gandhi, Kavita R., and Abdolreza Saadabadi. "Levodopa (L-Dopa)." StatPearls Publishing, 17 Apr. 2023, www.ncbi.nlm.nih.gov/books/NBK482140/. Accessed 11 Sept. 2024.
Liu, X., N. Lamango, and C. Charlton. "L-dopa Depletes S-adenosylmethionine and Increases S-adenosyl Homocysteine: Relationship to the Wearing Off Effects." Social Neuroscience, vol. 24, 1998, pp. 1469.
Sunagane, N., et al. "Possibility of Interactions Between Prescription Drugs and OTC Drugs (2nd Report): Interaction Between Levodopa Preparation and OTC Kampo Medicines for Upset Stomach." Yakugaku Zasshi, vol. 126, 2006, pp. 1191-1196.
"Taking Co-careldopa with Other Medicines and Herbal Supplements." NHS, www.nhs.uk/medicines/co-careldopa/taking-co-careldopa-with-other-medicines-and-herbal-supplements. Accessed 11 Sept. 2024.