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Effects of Vitamin C on Hyperoxia-Induced Reduction of Retinal Blood Flow

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ClinicalTrials.gov Identifier: NCT00712907
Recruitment Status : Completed
First Posted : July 10, 2008
Last Update Posted : July 10, 2008
Sponsor:
Information provided by:
Medical University of Vienna

Brief Summary:

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 or disease Intervention/treatment Phase
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 Not Applicable

Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 12 participants
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double (Participant, Investigator)
Primary Purpose: Diagnostic
Official Title: Effects of Vitamin C on Hyperoxia-Induced Reduction of Retinal Blood Flow
Study Start Date : February 2003
Actual Primary Completion Date : May 2003
Actual Study Completion Date : May 2003

Resource links provided by the National Library of Medicine

MedlinePlus related topics: Vitamin C
U.S. FDA Resources

Arm Intervention/treatment
Active Comparator: 1
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

Placebo Comparator: 2
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




Primary Outcome Measures :
  1. Retinal arterial and venous diameter (Zeiss retinal vessel analyzer) [ Time Frame: in total 6 hours ]
  2. Retinal blood flow velocity (laser Doppler velocimetry) [ Time Frame: in total 6 hours ]
  3. Intraocular pressure (applanation tonometry) [ Time Frame: in total 10 minutes ]


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Ages Eligible for Study:   19 Years to 35 Years   (Adult)
Sexes 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

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT00712907


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

Responsible Party: Gabriele Fuchsjäger-Mayrl, MD, Department of Clinical Pharmacology
ClinicalTrials.gov Identifier: NCT00712907     History of Changes
Other Study ID Numbers: OPHT-161202
First Posted: July 10, 2008    Key Record Dates
Last Update Posted: July 10, 2008
Last Verified: July 2008

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

Additional relevant MeSH terms:
Hyperoxia
Signs and Symptoms, Respiratory
Signs and Symptoms
Vitamins
Ascorbic Acid
Micronutrients
Growth Substances
Physiological Effects of Drugs
Antioxidants
Molecular Mechanisms of Pharmacological Action
Protective Agents