• Because dopamine itself does not naturally cross into the brain, it is often administered as levodopa (or L- Dopa), which passes into the brain where it is transformed into dopamine. Levodopa is usually given as a tablet or capsule.
  
  
• Levodopa is highly effective in controlling most symptoms of Parkinson's disease.
  More than 30 years after its discovery it remains the cornerstone of Parkinson's disease therapy, and a large majority of patients receive levodopa therapy.
  
  
• Failure to respond to levodopa may suggest that the disorder is not typical Parkinson's disease, but a Parkinson's disease- like disorder, and further medical assessments may be required.
  
  
• Once in the body, levodopa is broken down by molecules called enzymes - this reduces the amount of medication that can reach where it is needed in the brain.
  
  
• There are two main enzymes involved in the breakdown of levodopa: Peripheral dopa- decarboxylase (DDC) and catechol- O- methyltransferase (COMT).
  
  
• Inhibiting these enzymes can prevent levodopa's breakdown, optimizing it's availability in the brain and improving symptom control. Unfortunately the effectiveness of levodopa can decline after years of treatment.