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Completed

NCT Number: NCT00712907

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

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.

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Key information

Conditions

Ocular Physiology Regional Blood Flow

Age range

19 year–35 year

Sex eligibility

Male

Study type

Interventional

Phase

Not applicable

Primary location

Department of Clinical Pharmacology

Vienna, State of Vienna, 1090, Austria

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

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

Treatment and study plan

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

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

Placebo

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

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

Primary outcomes

  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

Sponsors and collaborators

Lead sponsor

Medical University of Vienna

Other

Registry information

Important dates

Study start
2003
Primary completion
2003
Study completion
2003
First posted
Jul 10, 2008
Registry last updated
Jul 10, 2008

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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