High and Low Dose Carbidopa Treatment of Parkinson's Disease
Condition: Parkinson's Disease
MeSH terms: Parkinson Disease
Intervention: carbidopa
Intervention description: 75 mg of carbidopa per day versus 450 mg of carbidopa per day
Intervention MeSH terms: Carbidopa
Phase: Phase 2
Study type: Interventional
Primary purpose: Treatment
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
Enrollment: 14.0
Sex: All
Minimum age: 35 Years
Maximum age: 85 Years
Healthy volunteers: No
Keywords: Parkinson's disease; Levodopa; Carbidopa; Blood brain barrier

Summary:

      Hypothesis: We hypothesize that carbidopa in daily doses of 450mg will enter the central
      nervous system and partially inhibit AAAD, thereby reducing the decarboxylation of exogenous
      levodopa to dopamine, and thereby blunt the therapeutic effects of levodopa in PD subjects.

      The purpose of this study is to see how low dose vs. high dose of the study drug, carbidopa
      effect movement in subjects with Parkinson's disease. The low dose of the study drug is 75 mg
      and the high dose is 450mg.

      Subjects will be recruited from the investigators clinic when they are seen for treatment for
      Parkinson's disease. Subjects will also be recruited through flyers hung at OHSU and at the
      VA.

      Subjects will take part in 2 screening visits one week apart to determine eligibility.
      Subjects will be randomly chosen to start either high or low dose carbidopa and take it for 4
      weeks. Subjects will be called 2, 4, and 6 or 7 days after this visit to ask how they are
      doing after starting this dose of study drug. We will leave them a message if we cannot reach
      them. If there are any problems, we will schedule them to come to the clinic within the next
      2 days.

      Subjects will have an outpatient visit 2 weeks after screening and a hospital admission 2
      weeks after that. At the hospital, subjects will stay for 3 days. They will have blood drawn
      and their Parkinson's disease assessed by a finger tapping exercise, timing their walking,
      and looking at their uncontrolled movements.

      The subject will then receive the opposite dose of carbidopa for 4 weeks. Subjects will be
      called 2, 4, and 6 or 7 days after this visit to ask how they are doing after starting this
      dose of study drug. We will leave them a message if we cannot reach them. If there are any
      problems, we will schedule them to come to the clinic within the next 2 days.

      The outpatient visit and hospital admission will repeat again. At the end of the second
      hospital admission, treatment on the study is over and subjects will go back to their
      original Parkinson's disease medications. The study will end with a follow up phone call or
      clinic visit 2 - 4 weeks after the final hospital admission.

      Subjects will fill out a daily diary that asks about their movement throughout the day for 3
      days before they come to the Oregon Clinical and Translational Research Institute.

      Carbidopa is used for the treatment of Parkinson's disease with levodopa. This protocol is
      using a high dose of 450mg of carbidopa. This study is also using IV levodopa, which is a
      different route than is normally given.

      Finger tapping rates will be compared between high and low dose study drug use to see if one
      group has slower rates than the other.
    

Eligibility criteria:

        Inclusion Criteria:

          -  Idiopathic Parkinson's disease

          -  Treatment with carbidopa/levodopa

          -  Motor fluctuations

        Exclusion Criteria:

          -  Dementia

          -  Hallucinations

          -  Age greater than 85