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

NCT ID: NCT00712907

Last Updated: 2008-07-10

Study Results

Results pending

The study team has not published outcome measurements, participant flow, or safety data for this trial yet. Check back later for updates.

Basic Information

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Recruitment Status

COMPLETED

Clinical Phase

NA

Total Enrollment

12 participants

Study Classification

INTERVENTIONAL

Study Start Date

2003-02-28

Study Completion Date

2003-05-31

Brief Summary

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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.

Detailed Description

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Conditions

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Ocular Physiology Regional Blood Flow

Keywords

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vitamin C retinal blood flow intraocular pressure retinal vessel diameter

Study Design

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Allocation Method

RANDOMIZED

Intervention Model

CROSSOVER

Primary Study Purpose

DIAGNOSTIC

Blinding Strategy

DOUBLE

Participants Investigators

Study Groups

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1

vitamin C (Mayrhofer)

Group Type ACTIVE_COMPARATOR

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

Intervention Type DIETARY_SUPPLEMENT

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

100% O2 (AGA) two times for 12 min

Intervention Type OTHER

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

Group Type PLACEBO_COMPARATOR

Placebo

Intervention Type DIETARY_SUPPLEMENT

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

100% O2 (AGA) two times for 12 min

Intervention Type OTHER

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

Interventions

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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

Intervention Type DIETARY_SUPPLEMENT

Placebo

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

Intervention Type DIETARY_SUPPLEMENT

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

Intervention Type OTHER

Eligibility Criteria

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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
Minimum Eligible Age

19 Years

Maximum Eligible Age

35 Years

Eligible Sex

MALE

Accepts Healthy Volunteers

Yes

Sponsors

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Medical University of Vienna

OTHER

Sponsor Role lead

Responsible Party

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Department of Clinical Pharmacology

Locations

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Department of Clinical Pharmacology

Vienna, Vienna, Austria

Site Status

Countries

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Austria

Other Identifiers

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OPHT-161202

Identifier Type: -

Identifier Source: org_study_id