Kidney Dopamine Effects on Urinary Sodium Excretion in Postural Tachycardia Syndrome
试验速览
- 阶段
- 2 期
- 状态
- 已完成
- 入组人数
- 32
- 试验地点
- 1
- 主要终点
- 24 Hour Urinary Sodium Excretion During Treatment Normalized to Creatinine
研究概览
简要总结
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.
详细描述
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 the night. However, they will need to consume the 200 mEq/day study diet for each meal, collect all urine, and take study medication on schedule
- After returning to the CRC, the subjects will fast after 7 pm.
- In the morning, supine and standing heart rate and blood pressure will be recorded, and the subjects will be asked to collect their urine to end the 24hr urine collection.
- The final dose of study medication (Carbidopa 200mg or placebo) will be given orally following the void, at approximately 7 am.
- Supine heart rate and blood pressure will be measured and supine blood samples will be collected hourly for 4 hours after the treatment and at 8 hours after the treatment. Subjects must rest supine for at least 30 minutes before each blood draw.
- At 2 hours after treatment, subjects will stand for 10 minutes for upright blood pressure and heart rate measurements and collection of an upright blood sample, as described above. Participants will be asked to rate the severity of common orthostatic symptoms while supine and upright.
- Urine will be collected for two 4-hour periods after treatment and from 8 hours to 24 hours after treatment.
- Fixed-sodium study diet will be provided after the 4-hour measurements and in the evening.
After at least a 1 day washout period, the study will be repeated with Treatment B
研究设计
- 研究类型
- Interventional
- 分配方式
- Randomized
- 干预模型
- Crossover
- 主要目的
- Other
- 盲法
- Single (Participant)
入排标准
- 年龄范围
- 18 Years 至 60 Years（Adult）
- 性别
- All
- 接受健康志愿者
- 是
入选标准
- •Patients diagnosed with POTS by the Vanderbilt Autonomic Dysfunction Center based on the following stringent criteria: 1) history of daily orthostatic symptoms for at least 6 months; 2) increase in heart rate (HR) of at least 30 bpm with standing or a standing HR of at least 120 bpm; 3) absence of orthostatic hypotension (defined as a fall in blood pressure (BP)>20/10 mm Hg); and 4) absence of conditions, such as dehydration, substantial weight loss, or systemic illnesses, that could provoke orthostatic intolerance
- •Upright plasma NE at least 600 pg/mL in patients
- •Non-smoking
- •Free of medications with the potential to influence BP
- •Able and willing to provide informed consent -
排除标准
- •Overt cause for postural tachycardia (such as acute dehydration)
- •Significant cardiovascular, pulmonary, hepatic, or hematological disease by history or screening results
- •Positive urine b-hcg pregnancy test
- •Evidence of cardiac structural disease (by clinical examination or prior echocardiogram)
- •Hypertension defined as a BP>145/95 (off medications) or need for antihypertensive medications
- •Evidence of significant conduction system delay (QRS duration >120 ms) on electrocardiogram
- •Inability to give, or withdraw, informed consent
研究组 & 干预措施
Carbidopa then Placebo
Carbidopa 200 mg every 6 hours orally for 5 doses followed by Placebo every 6 hours for 5 doses
干预措施: Placebo (Drug)
Carbidopa then Placebo
Carbidopa 200 mg every 6 hours orally for 5 doses followed by Placebo every 6 hours for 5 doses
干预措施: Carbidopa (Drug)
Placebo then Carbidopa
Placebo matching carbidopa given every 6 hours orally for 5 doses followed by Carbidopa
干预措施: Carbidopa (Drug)
Placebo then Carbidopa
Placebo matching carbidopa given every 6 hours orally for 5 doses followed by Carbidopa
干预措施: Placebo (Drug)
结局指标
主要结局
24 Hour Urinary Sodium Excretion During Treatment Normalized to Creatinine
时间窗: Immediately before the 1st dose of placebo or carbidopa to immediately before the 5th dose (approximately 24 hours)
Urine was collected for 24hr during treatment. Urinary volume was measured and the urine was analyzed for sodium and creatinine concentrations. Total amounts of sodium and creatinine excreted over the 24 hr were calculated and results expressed as ratio of sodium:creatinine.
次要结局
- 24 Hour Urinary Catecholamine (Dopamine) Excretion During Treatment Normalized to Creatinine(Immediately before the 1st dose of Placebo or Carbidopa and ending immediately before the last dose (approximately 24 hours))
- Systolic Blood Pressure Measured at 8 Hours After the Last Dose of Placebo or Carbidopa(8 hours after the last dose of placebo or carbidopa)
- Supine Plasma Renin Activity 2 Hours After the Last Dose of Placebo or Carbidopa(2 hours after the last dose of placebo or carbidopa)
- 24 Hour Urinary Catecholamine (DOPA) Excretion During Treatment Normalized to Creatinine(Immediately before the 1st dose of Placebo or Carbidopa and ending immediately before the last dose (approximately 24 hours))
- Plasma Catecholamines (Norepinephrine) After the Last Dose of Placebo or Carbidopa(8 hours after the last dose of placebo or carbidopa)
- Plasma Catecholamines (DOPA) After the Last Dose of Placebo or Carbidopa(8 hours after the last dose of placebo or carbidopa)
- Plasma Sodium After the Last Dose of Placebo or Carbidopa(8 hours after the last dose of placebo or carbidopa)
研究者
Alfredo Gamboa
Research Associate Professor of Medicine
Vanderbilt University