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

Primary Purpose

Ocular Physiology, Regional Blood Flow

Status
Completed
Phase
Not Applicable
Locations
Austria
Study Type
Interventional
Intervention
vitamin C (Mayrhofer) 24mg/min i.v. for 64 min
Placebo
100% O2 (AGA) two times for 12 min
Sponsored by
Medical University of Vienna
About
Eligibility
Locations
Arms
Outcomes
Full info

About this trial

This is an interventional diagnostic trial for Ocular Physiology focused on measuring vitamin C, retinal blood flow, intraocular pressure, retinal vessel diameter

Eligibility Criteria

19 Years - 35 Years (Adult)MaleAccepts Healthy Volunteers

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

Sites / Locations

  • Department of Clinical Pharmacology

Arms of the Study

Arm 1

Arm 2

Arm Type

Active Comparator

Placebo Comparator

Arm Label

1

2

Arm Description

vitamin C (Mayrhofer)

Placebo

Outcomes

Primary Outcome Measures

Retinal arterial and venous diameter (Zeiss retinal vessel analyzer)
Retinal blood flow velocity (laser Doppler velocimetry)
Intraocular pressure (applanation tonometry)

Secondary Outcome Measures

Full Information

First Posted
July 8, 2008
Last Updated
July 9, 2008
Sponsor
Medical University of Vienna
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1. Study Identification

Unique Protocol Identification Number
NCT00712907
Brief Title
Effects of Vitamin C on Hyperoxia-Induced Reduction of Retinal Blood Flow
Official Title
Effects of Vitamin C on Hyperoxia-Induced Reduction of Retinal Blood Flow
Study Type
Interventional

2. Study Status

Record Verification Date
July 2008
Overall Recruitment Status
Completed
Study Start Date
February 2003 (undefined)
Primary Completion Date
May 2003 (Actual)
Study Completion Date
May 2003 (Actual)

3. Sponsor/Collaborators

Name of the Sponsor
Medical University of Vienna

4. Oversight

Data Monitoring Committee
Yes

5. Study Description

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.

6. Conditions and Keywords

Primary Disease or Condition Being Studied in the Trial, or the Focus of the Study
Ocular Physiology, Regional Blood Flow
Keywords
vitamin C, retinal blood flow, intraocular pressure, retinal vessel diameter

7. Study Design

Primary Purpose
Diagnostic
Study Phase
Not Applicable
Interventional Study Model
Crossover Assignment
Masking
ParticipantInvestigator
Allocation
Randomized
Enrollment
12 (Actual)

8. Arms, Groups, and Interventions

Arm Title
1
Arm Type
Active Comparator
Arm Description
vitamin C (Mayrhofer)
Arm Title
2
Arm Type
Placebo Comparator
Arm Description
Placebo
Intervention Type
Dietary Supplement
Intervention Name(s)
vitamin C (Mayrhofer) 24mg/min i.v. for 64 min
Intervention Description
Substance: Ascorbic acid (Mayrhofer) Manufacturer: Mayrhofer, Linz, Austria Dosage form: i.v. Dosage: 24mg/min over 64 min Dosage reference: Ting HH 1996
Intervention Type
Dietary Supplement
Intervention Name(s)
Placebo
Intervention Description
Substance: Physiologic saline solution 0.9% (placebo) Dosage form: i.v. Dosage: 24ml/min over 64 min
Intervention Type
Other
Intervention Name(s)
100% O2 (AGA) two times for 12 min
Intervention Description
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 Measure Information:
Title
Retinal arterial and venous diameter (Zeiss retinal vessel analyzer)
Time Frame
in total 6 hours
Title
Retinal blood flow velocity (laser Doppler velocimetry)
Time Frame
in total 6 hours
Title
Intraocular pressure (applanation tonometry)
Time Frame
in total 10 minutes

10. Eligibility

Sex
Male
Minimum Age & Unit of Time
19 Years
Maximum Age & Unit of Time
35 Years
Accepts Healthy Volunteers
Accepts Healthy Volunteers
Eligibility 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
Facility Information:
Facility Name
Department of Clinical Pharmacology
City
Vienna
ZIP/Postal Code
1090
Country
Austria

12. IPD Sharing Statement

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

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