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Effects of Vitamin C on Hyperoxia-Induced Reduction of Retinal Blood Flow
This study has been completed.
First Received: July 8, 2008   Last Updated: July 9, 2008   History of Changes
Sponsored by: Medical University of Vienna
Information provided by: Medical University of Vienna
ClinicalTrials.gov Identifier: NCT00712907
  Purpose

High arterial blood oxygen tension leads to vasoconstriction of retinal vessels, possibly related to an interaction between reactive oxygen species and endothelium-derived vasoactive factors. Vitamin C is a potent antioxidant capable of reversing endothelial dysfunction due to increased oxidant stress.

Vitamin C appears to have vasodilatory properties, but the underlying mechanisms are not well understood.

In the present study we hypothesized that hyperoxic vasoconstriction of retinal vessels could be diminished by vitamin C.

Ocular blood flow will be determined by non-invasive methods, including laser Doppler velocimetry and the Zeiss retinal vessel analyser.


Condition Intervention
Ocular Physiology
Regional Blood Flow
 Dietary Supplement: vitamin C (Mayrhofer) 24mg/min i.v. for 64 min
Dietary Supplement: Placebo
Other: 100% O2 (AGA) two times for 12 min

MedlinePlus related topics: Dietary Supplements Diets
Drug Information available for: Ascorbic acid
U.S. FDA Resources
Study Type: Interventional
Study Design: Diagnostic, Randomized, Double Blind (Subject, Investigator), Crossover Assignment, Safety/Efficacy Study
Official Title: Effects of Vitamin C on Hyperoxia-Induced Reduction of Retinal Blood Flow

Further study details as provided by Medical University of Vienna:

Primary Outcome Measures:
  • Retinal arterial and venous diameter (Zeiss retinal vessel analyzer) [ Time Frame: in total 6 hours ] [ Designated as safety issue: No ]
  • Retinal blood flow velocity (laser Doppler velocimetry) [ Time Frame: in total 6 hours ] [ Designated as safety issue: No ]
  • Intraocular pressure (applanation tonometry) [ Time Frame: in total 10 minutes ] [ Designated as safety issue: No ]

Enrollment: 12
Study Start Date: February 2003
Study Completion Date: May 2003
Primary Completion Date: May 2003 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
1: Active Comparator
vitamin C (Mayrhofer)
Dietary Supplement: vitamin C (Mayrhofer) 24mg/min i.v. for 64 min
Substance: Ascorbic acid (Mayrhofer) Manufacturer: Mayrhofer, Linz, Austria Dosage form: i.v. Dosage: 24mg/min over 64 min Dosage reference: Ting HH 1996
Other: 100% O2 (AGA) two times for 12 min

Substance: 100% oxygen (AGA, Vienna, Austria, gases for human use) Manufacturer: AGA, Vienna, Austria, gases for human use Dosage form: Inhalation through an oxygenmask over a period of 12 minutes two times per study day.

Dosage reference: Strenn K 1997
2: Placebo Comparator
Placebo
Dietary Supplement: Placebo
Substance: Physiologic saline solution 0.9% (placebo) Dosage form: i.v. Dosage: 24ml/min over 64 min
Other: 100% O2 (AGA) two times for 12 min

Substance: 100% oxygen (AGA, Vienna, Austria, gases for human use) Manufacturer: AGA, Vienna, Austria, gases for human use Dosage form: Inhalation through an oxygenmask over a period of 12 minutes two times per study day.

Dosage reference: Strenn K 1997

  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 A 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, ametropia < 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: NCT00712907

Locations
Austria
Department of Clinical Pharmacology
Vienna, Austria, 1090
Sponsors and Collaborators
Medical University of Vienna
  More Information

No publications provided

Responsible Party: Department of Clinical Pharmacology ( Gabriele Fuchsjäger-Mayrl, MD )
Study ID Numbers: OPHT-161202
Study First Received: July 8, 2008
Last Updated: July 9, 2008
ClinicalTrials.gov Identifier: NCT00712907     History of Changes
Health Authority: Austria: Agency for Health and Food Safety

Keywords provided by Medical University of Vienna:
vitamin C
retinal blood flow
intraocular pressure
retinal vessel diameter

Study placed in the following topic categories:
Hyperoxia
Antioxidants
Vitamins
 Trace Elements
Micronutrients
Ascorbic Acid

Additional relevant MeSH terms:
Antioxidants
Molecular Mechanisms of Pharmacological Action
Growth Substances
Vitamins
Physiological Effects of Drugs
 Micronutrients
Protective Agents
Pharmacologic Actions
Ascorbic Acid

ClinicalTrials.gov processed this record on May 07, 2009



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