Levodropropizine Products | Cleanchem - Levodopa is the metabolic precursor of dopamine and is the cornerstone treatment for Parkinson? disease. It crosses the blood-brain barrier and is converted to dopamine in the brain, replenishing diminished levels. It is often combined with a dopa decarboxylase inhibitor (like carbidopa) to prevent peripheral conversion. Long-term use can lead to motor fluctuations and dyskinesias.