NCT00712907

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.

Trial Health

87
On Track

Trial Health Score

Automated assessment based on enrollment pace, timeline, and geographic reach

Enrollment
12

participants targeted

Target at below P25 for not_applicable

Timeline
Completed

Started Feb 2003

Shorter than P25 for not_applicable

Geographic Reach
1 country

1 active site

Status
completed

Health score is calculated from publicly available data and should be used for screening purposes only.

Trial Relationships

Click on a node to explore related trials.

Study Timeline

Key milestones and dates

Study Start

First participant enrolled

February 1, 2003

Completed
3 months until next milestone

Primary Completion

Last participant's last visit for primary outcome

May 1, 2003

Completed
Same day until next milestone

Study Completion

Last participant's last visit for all outcomes

May 1, 2003

Completed
5.2 years until next milestone

First Submitted

Initial submission to the registry

July 8, 2008

Completed
2 days until next milestone

First Posted

Study publicly available on registry

July 10, 2008

Completed
Last Updated

July 10, 2008

Status Verified

July 1, 2008

Enrollment Period

3 months

First QC Date

July 8, 2008

Last Update Submit

July 9, 2008

Conditions

Ocular PhysiologyRegional Blood Flow

Keywords

vitamin Cretinal blood flowintraocular pressureretinal vessel diameter

Outcome Measures

Primary Outcomes (3)

  • Retinal arterial and venous diameter (Zeiss retinal vessel analyzer)

    in total 6 hours

  • Retinal blood flow velocity (laser Doppler velocimetry)

    in total 6 hours

  • Intraocular pressure (applanation tonometry)

    in total 10 minutes

Study Arms (2)

1

ACTIVE COMPARATOR

vitamin C (Mayrhofer)

Dietary Supplement: vitamin C (Mayrhofer) 24mg/min i.v. for 64 minOther: 100% O2 (AGA) two times for 12 min

2

PLACEBO COMPARATOR

Placebo

Dietary Supplement: PlaceboOther: 100% O2 (AGA) two times for 12 min

Interventions

vitamin C (Mayrhofer) 24mg/min i.v. for 64 minDIETARY_SUPPLEMENT

Substance: Ascorbic acid (Mayrhofer) Manufacturer: Mayrhofer, Linz, Austria Dosage form: i.v. Dosage: 24mg/min over 64 min Dosage reference: Ting HH 1996

1
PlaceboDIETARY_SUPPLEMENT

Substance: Physiologic saline solution 0.9% (placebo) Dosage form: i.v. Dosage: 24ml/min over 64 min

2
100% O2 (AGA) two times for 12 minOTHER

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

12

Eligibility Criteria

Age19 Years - 35 Years
Sexmale
Healthy VolunteersYes
Age GroupsAdult (18-64)

You may qualify if:

  • 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.

You may not qualify if:

  • 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

Contact the study team to confirm eligibility.

Sponsors & Collaborators

Study Sites (1)

Department of Clinical Pharmacology

Vienna, Vienna, 1090, Austria

Location

MeSH Terms

Interventions

Ascorbic Acid

Intervention Hierarchy (Ancestors)

Sugar AcidsAcids, AcyclicCarboxylic AcidsOrganic ChemicalsHydroxy AcidsCarbohydrates

Study Design

Study Type
interventional
Phase
not applicable
Allocation
RANDOMIZED
Masking
DOUBLE
Who Masked
PARTICIPANT, INVESTIGATOR
Purpose
DIAGNOSTIC
Intervention Model
CROSSOVER
Sponsor Type
OTHER

Study Record Dates

First Submitted

July 8, 2008

First Posted

July 10, 2008

Study Start

February 1, 2003

Primary Completion

May 1, 2003

Study Completion

May 1, 2003

Last Updated

July 10, 2008

Record last verified: 2008-07

Locations

AU(1)