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Sponsored by: |
Medical University of Vienna |
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Information provided by: | Medical University of Vienna |
ClinicalTrials.gov Identifier: | NCT00280462 |
Autoregulation is the ability of a vascular bed to maintain blood flow despite changes in perfusion pressure. For a long time it had been assumed that the choroid is a strictly passive vascular bed, which shows no autoregulation. However, recently several groups have identified some autoregulatory capacity of the human choroid. In the brain and the retina the mechanism behind autoregulation is most likely linked to changes in transmural pressure.
In this model arterioles change their vascular tone depending on the pressure inside the vessel and outside the vessel. In the choroid, several observations argue against a direct involvement of arterioles. In a previous project we were able to identify that the nitric oxide (NO) - system as well as the endothelin system are involved in choroidal blood flow regulation during isometric exercise.
In the present study autoregulation of the choroid during isometric exercise will be investigated and the pressure/flow relationships will be observed in the absence or presence of a calcium antagonist - nifedipine.
Condition | Intervention |
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Ocular Physiology Regional Blood Flow |
Drug: Nifedipine (drug) Drug: L-Arginin (drug) Drug: Placebo |
Study Type: | Interventional |
Study Design: | Treatment, Randomized, Double Blind (Subject, Investigator), Placebo Control, Crossover Assignment, Safety/Efficacy Study |
Official Title: | Choroidal Blood Flow Regulation During Isometric Exercise: Effects of Ca2+-Channel Blockade |
Enrollment: | 21 |
Study Start Date: | August 2005 |
Study Completion Date: | April 2006 |
Primary Completion Date: | April 2006 (Final data collection date for primary outcome measure) |
Arms | Assigned Interventions |
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1: Active Comparator
Nifedipine
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Drug: Nifedipine (drug)
Nifedipine (Adalat®, Bayer, Leverkusen, Germany) dose: 15µg/kg bolus infusion over 5 minutes; 0.2 µg/(kg.min) maintenance dose infusion period 25 minutes
Drug: L-Arginin (drug)
L-Arginin (Clinalfa AG, Läufelfingen, Switzerland) 30% sodium chlorid solution, dose: 1g/min over 30 minutes
Drug: Placebo
Placebo
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2: Active Comparator
L-Arginin
|
Drug: Nifedipine (drug)
Nifedipine (Adalat®, Bayer, Leverkusen, Germany) dose: 15µg/kg bolus infusion over 5 minutes; 0.2 µg/(kg.min) maintenance dose infusion period 25 minutes
Drug: L-Arginin (drug)
L-Arginin (Clinalfa AG, Läufelfingen, Switzerland) 30% sodium chlorid solution, dose: 1g/min over 30 minutes
Drug: Placebo
Placebo
|
3: Placebo Comparator
Placebo
|
Drug: Nifedipine (drug)
Nifedipine (Adalat®, Bayer, Leverkusen, Germany) dose: 15µg/kg bolus infusion over 5 minutes; 0.2 µg/(kg.min) maintenance dose infusion period 25 minutes
Drug: L-Arginin (drug)
L-Arginin (Clinalfa AG, Läufelfingen, Switzerland) 30% sodium chlorid solution, dose: 1g/min over 30 minutes
Drug: Placebo
Placebo
|
Ages Eligible for Study: | 19 Years to 35 Years |
Genders Eligible for Study: | Male |
Accepts Healthy Volunteers: | Yes |
Inclusion Criteria:
Exclusion Criteria:
Austria | |
Department of Clinical Pharmacology | |
Vienna, Austria, 1090 |
Principal Investigator: | Gabriele Fuchsjäger-Mayrl, M.D. | Department of Clinical Pharmacology, Medical University of Vienna |
Responsible Party: | Department of Clinical Pharmacology, Medical University of Vienna ( Gabriele Fuchsjaeger-Mayrl, MD ) |
Study ID Numbers: | OPHT-110705 |
Study First Received: | January 19, 2006 |
Last Updated: | July 8, 2008 |
ClinicalTrials.gov Identifier: | NCT00280462 History of Changes |
Health Authority: | Austria: Federal Ministry for Health and Women |
Nifedipine Choroidal blood flow Choroidal autoregulation Isometric exercise |
Calcium, Dietary Vasodilator Agents Calcium Channel Blockers Cardiovascular Agents Nifedipine |
Membrane Transport Modulators Vasodilator Agents Tocolytic Agents Molecular Mechanisms of Pharmacological Action Therapeutic Uses Physiological Effects of Drugs |
Calcium Channel Blockers Reproductive Control Agents Cardiovascular Agents Nifedipine Pharmacologic Actions |