Choroidal Blood Flow Regulation During Isometric Exercise: Effects of Ca2+-Channel Blockade

This study has been completed.
Sponsor:
Information provided by:
Medical University of Vienna
ClinicalTrials.gov Identifier:
NCT00280462
First received: January 19, 2006
Last updated: July 8, 2008
Last verified: July 2008
  Purpose

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
Ocular Physiology
Regional Blood Flow
Drug: Nifedipine (drug)
Drug: L-Arginin (drug)
Drug: Placebo

Study Type: Interventional
Study Design: Allocation: Randomized
Endpoint Classification: Safety/Efficacy Study
Intervention Model: Crossover Assignment
Masking: Double Blind (Subject, Investigator)
Primary Purpose: Treatment
Official Title: Choroidal Blood Flow Regulation During Isometric Exercise: Effects of Ca2+-Channel Blockade

Resource links provided by NLM:


Further study details as provided by Medical University of Vienna:

Primary Outcome Measures:
  • Choroidal pressure-blood flow relationship [ Time Frame: in total 3x 3 hours ] [ Designated as safety issue: No ]

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
Active Comparator: 1
Nifedipine
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
Active Comparator: 2
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
Placebo Comparator: 3
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

  Eligibility

Ages Eligible for Study:   19 Years to 35 Years
Genders Eligible for Study:   Male
Accepts Healthy Volunteers:   Yes
Criteria

Inclusion Criteria:

  • Men aged between 19 and 35 years, nonsmokers
  • Body mass index between 15th and 85th percentile (Must et al. 1991)
  • Normal findings in the medical history and physical examination unless the investigator considers an abnormality to be clinically irrelevant
  • Normal laboratory values unless the investigator considers an abnormality to be clinically irrelevant
  • Normal ophthalmic findings, ametropy more than 3 Dpt.

Exclusion Criteria:

  • Regular use of medication, abuse of alcoholic beverages, participation in a clinical trial in the 3 weeks preceding the study
  • Treatment in the previous 3 weeks with any drug
  • Symptoms of a clinically relevant illness in the 3 weeks before the first study day
  • History of hypersensitivity to the trial drug or to drugs with a similar chemical structure
  • History or presence of gastrointestinal, liver or kidney disease, or other conditions known to interfere with, distribution, metabolism or excretion of study drugs
  • Blood donation during the previous 3 weeks
  Contacts and Locations
Please refer to this study by its ClinicalTrials.gov identifier: NCT00280462

Locations
Austria
Department of Clinical Pharmacology
Vienna, Austria, 1090
Sponsors and Collaborators
Medical University of Vienna
Investigators
Principal Investigator: Gabriele Fuchsjäger-Mayrl, M.D. Department of Clinical Pharmacology, Medical University of Vienna
  More Information

No publications provided by Medical University of Vienna

Additional publications automatically indexed to this study by ClinicalTrials.gov Identifier (NCT Number):
Responsible Party: Gabriele Fuchsjaeger-Mayrl, MD, Department of Clinical Pharmacology, Medical University of Vienna
ClinicalTrials.gov Identifier: NCT00280462     History of Changes
Other Study ID Numbers: OPHT-110705
Study First Received: January 19, 2006
Last Updated: July 8, 2008
Health Authority: Austria: Federal Ministry for Health and Women

Keywords provided by Medical University of Vienna:
Nifedipine
Choroidal blood flow
Choroidal autoregulation
Isometric exercise

Additional relevant MeSH terms:
Nifedipine
Tocolytic Agents
Reproductive Control Agents
Physiological Effects of Drugs
Pharmacologic Actions
Therapeutic Uses
Calcium Channel Blockers
Membrane Transport Modulators
Molecular Mechanisms of Pharmacological Action
Cardiovascular Agents
Vasodilator Agents

ClinicalTrials.gov processed this record on April 15, 2014