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

Not Applicable

Completed

• Conditions: Ocular Physiology; Regional Blood Flow
• Interventions: Dietary Supplement: vitamin C (Mayrhofer) 24mg/min i.v. for 64 min; Dietary Supplement: Placebo; Other: 100% O2 (AGA) two times for 12 min

• Registration Number: NCT00712907
• Lead Sponsor: Medical University of Vienna

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.

Detailed Description

Not available

Study Timeline

• Study Start: 2003-02
• Primary Completion: 2003-05
• Study Completion: 2003-05
• Status Verified: 2008-07
• Study First Submitted: 2008-07-08
• Study First Submitted QC: 2008-07-09
• Last Update Submitted: 2008-07-09
• Study First Posted: 2008-07-10
• Last Update Posted: 2008-07-10

Recruitment & Eligibility

• Status: COMPLETED
• Sex: Male
• Target Recruitment: 12

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

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: CROSSOVER

Arm && Interventions

Group	Intervention	Description
1	vitamin C (Mayrhofer) 24mg/min i.v. for 64 min	vitamin C (Mayrhofer)
1	100% O2 (AGA) two times for 12 min	vitamin C (Mayrhofer)
2	Placebo	Placebo
2	100% O2 (AGA) two times for 12 min	Placebo

Primary Outcome Measures

Name	Time	Method
Retinal arterial and venous diameter (Zeiss retinal vessel analyzer)	in total 6 hours
Intraocular pressure (applanation tonometry)	in total 10 minutes
Retinal blood flow velocity (laser Doppler velocimetry)	in total 6 hours

Trial Locations

Locations (1)

Department of Clinical Pharmacology; 🇦🇹 Vienna, Austria