Known brand names include Sinemet, Rytary, Crexont, Duopa, Dhivy, and Vyalev.
The main oral treatment for Parkinson's disease. Levodopa is turned into dopamine in the brain, and carbidopa keeps it from being used up in the rest of the body. It eases slowness, stiffness, and tremor, but involuntary movements, wearing off between doses, low blood pressure on standing, and hallucinations can develop.
Labeled use. Parkinson's disease, post-encephalitic parkinsonism, and parkinsonism after carbon monoxide or manganese intoxication.
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The most effective symptomatic therapy for Parkinson's disease and the usual first choice when motor symptoms affect function, especially in older patients. Dopamine agonists and MAO-B inhibitors may be used first in some younger patients to delay motor fluctuations, at the cost of more impulse control problems. Avoid typical antipsychotics and metoclopramide in Parkinson's disease because they block dopamine.
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Parkinson's symptoms reflect striatal dopamine depletion. Levodopa, the metabolic precursor of dopamine, crosses the blood-brain barrier and is presumably converted to dopamine in the brain. Carbidopa inhibits peripheral dopa decarboxylase but does not cross the blood-brain barrier, so more levodopa reaches the brain, less peripheral dopamine causes nausea, and the levodopa dose falls by about 75%. Levodopa's half-life rises from about 50 minutes to about 1.5 hours with carbidopa. Dietary protein competes with levodopa for absorption.
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The label does not describe a narrow therapeutic index or direct dosing by measured blood levels of the drug.
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Doses come from the FDA label. Study tool, not for clinical decisions.
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No specific antidote; pyridoxine does not reverse it. Give supportive care with judicious IV fluids, maintain the airway, and monitor the ECG for arrhythmias, treating them as needed. The value of dialysis is unknown.
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No adequate human studies. It caused malformations in rabbits, and levodopa crosses the human placenta. Weigh the expected benefit against possible hazards to mother and child.
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Safety and effectiveness have not been established, and use under 18 is not recommended.
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No overall differences in trials, but some older adults may be more sensitive to adverse effects such as hallucinations. It is titrated to effect without a specific age-based dose.
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