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

Sponsor

Medical University of Vienna (Other)

Overall Status

Completed

CT.gov ID

NCT00712907

Collaborator

(none)

Enrollment

Location

Arms

2.9

Duration (Months)

4.1

Patients Per Site Per Month

Study Details

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.

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	N/A

Study Design

Study Type:

Interventional

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 :

Feb 1, 2003

Actual Primary Completion Date :

May 1, 2003

Actual Study Completion Date :

May 1, 2003

Arms and Interventions

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

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

Outcome Measures

Primary Outcome Measures

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]

Eligibility Criteria

Criteria

Ages Eligible for Study:

19 Years to 35 Years

Sexes Eligible for Study:

Male

Accepts Healthy Volunteers:

Yes

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