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Levodopa

Also indexed as: Dopar®, Larodopa®, L-dopa

Levodopa is the precursor required by the brain to produce dopamine, a neurotransmitter (chemical messenger in the nervous system). People with Parkinson’s disease have depleted levels of dopamine. Levodopa is used to increase dopamine in the brain, which reduces the symptoms of Parkinson’s disease. Levodopa is broken down by the body before it reaches the brain. To avoid this, levodopa is used with carbidopa, a drug that protects levodopa from breakdown. Levodopa is available alone or in a combination product.

Interactions with Dietary Supplements

Vitamin B6
Levodopa is broken down in the body by a process requiring vitamin B6. Breakdown may deplete available vitamin B6. Carbidopa blocks levodopa breakdown and prevents vitamin B6 depletion. People taking levodopa/carbidopa (Sinemet®), or levodopa plus carbidopa (Lodosyn®) have no risk for levodopa-induced vitamin B6 deficiency; it is not a problem for people to supplement vitamin B6 while taking Sinemet.

For people taking levodopa alone, small amounts of vitamin B6 (5–10 mg per day) may prevent levodopa-induced vitamin B6 deficiency.1 Amounts of vitamin B6 slightly higher than those required to replace depleted levels, may reduce the effectiveness of levodopa therapy and should not be taken.2

Interactions with Foods and Other Compounds

Food
Food, especially foods high in protein, compete with levodopa for absorption. However, levodopa may be taken with food to avoid stomach upset.3 It is important to take levodopa at the same time every day, always with or always without food. People with questions about levodopa and food should ask their prescribing doctor or pharmacist. Taking sustained-release Sinemet® CR with food may increase blood levels of levodopa.4 It is important to take Sinemet® CR at the same time every day, always with or always without food. People with questions about Sinemet® CR and food should ask their prescribing doctor or pharmacist.

Summary of Interactions for Levodopa

Depletion or interference Vitamin B6
Adverse interaction None known
Side effect reduction/prevention None known
Supportive interaction None known
Reduced drug absorption/bioavailability None known

For the convenience of the reader, the information in the summary is categorized as follows: “Depletion or interference” indicates the drug may deplete or interfere with the absorption or function of the supplement or herb. “Adverse interaction” indicates that the supplement or herb used together with the drug may result in undesirable effects. “Side effect reduction/prevention” indicates the supplement or herb may reduce the likelihood and/or severity of a potential side effect caused by the drug. “Supportive interaction” indicates the supplement or herb may support or aid the function of the drug. “Reduced drug absorption/bioavailability” indicates that the supplement or herb may decrease the absorption and/or activity of the drug in the body. An asterisk (*) next to an item in the summary indicates that the interaction is supported only by weak, fragmentary, and/or contradictory scientific evidence.

References:

1. Long JW. The Essential Guide to Prescription Drugs 1992. New York: Harper Perennial, 1991.

2. Trovato A et al. Drug-nutrient interactions. Am Family Phys 1991;44:1651–8.

3. Threlkeld DS, ed. Central Nervous System Drugs, Antiparkinson Agents, Levodopa. In Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons, Sep 1991, 289p–290a.

4. Threlkeld DS, ed. Central Nervous System Drugs, Antiparkinson Agents, Levodopa. In Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons, Sep 1991, 289p–290a.