Clinical Trial: Peripheral Dopamine in Postural Tachycardia Syndrome

Study Status: Active, not recruiting
Recruit Status: Active, not recruiting
Study Type: Interventional

Official Title: Kidney Dopamine Effects on Urinary Sodium Excretion in Postural Tachycardia Syndrome

Brief Summary: The purpose of the proposed research is to determine how changes in kidney dopamine (DA) activity influence urinary sodium excretion. We will decrease DA activity in the kidney by inhibiting DA synthesis via carbidopa administration. We want to compare findings in normal volunteers and in patients with postural tachycardia syndrome (POTS). We will test the null hypothesis (Ho) that the effects of oral carbidopa administration on urinary sodium excretion will not differ between patients with POTS and healthy volunteers.

Detailed Summary:

We will determine whether inhibition of renal dopamine formation by carbidopa administration leads to a decrease in urinary excretion of dopamine and sodium and whether the response differs in POTS and control populations. Carbidopa effects will be compared to those of a matching placebo, and the sequence of treatments (carbidopa before placebo or placebo before carbidopa) will be randomized.

Each subject will undergo a complete history and physical examination, including an electrocardiogram (EKG).

  • After achieving sodium balance on a 200 mEq/day sodium diet, subjects will collect urine over 24hr for baseline assessment of sodium and catecholamines.
  • On this day, the subjects will be admitted to the CRC.
  • An 18 gauge intravenous catheter will be inserted in order to draw blood.
  • The subjects will fast from 7 pm until after the next morning's testing.
  • In the morning, while still supine after the overnight sleep, heart rate and blood pressure will be recorded, and blood will be drawn. The subjects will then stand for 10 minutes. Heart rate and blood pressure will be measured at intervals, and an upright blood sample will be collected.
  • The subjects will be asked to collect their urine to end the 24hr urine collection. Another 24hr urine collection will be started.
  • Treatment A (Carbidopa 200mg or placebo) will be given orally following the void, at approximately 7 am. Additional doses will be taken every 6 hours with the last dose at 7 am the following morning.
  • Subjects will be free to follow their normal routine during the day until returning to the CRC for
    Sponsor: Vanderbilt University

    Current Primary Outcome: The primary outcome is the urinary sodium concentration normalized to creatinine. [ Time Frame: 24 hours ]

    Original Primary Outcome: Same as current

    Current Secondary Outcome:

    • Blood pressure [ Time Frame: 8 hours ]
    • Plasma catecholamines [ Time Frame: 8 hours ]
    • Urinary catecholamines [ Time Frame: 24 hours ]
    • Plasma renin activity [ Time Frame: 2 hours ]
    • Plasma sodium [ Time Frame: 8 hours ]


    Original Secondary Outcome: Same as current

    Information By: Vanderbilt University Medical Center

    Dates:
    Date Received: May 27, 2008
    Date Started: May 2008
    Date Completion: October 2017
    Last Updated: April 3, 2017
    Last Verified: April 2017