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

Regional Blood Flow Clinical Trial

Official title:

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

Clinical Trial Details — Status: Completed

Administrative data

• NCT number: NCT00712907
• Other study ID #: OPHT-161202
• Status: Completed
• Phase: N/A
• First received: July 8, 2008
• Last updated: July 9, 2008
• Start date: February 2003
• Est. completion date: May 2003

Study information

• Verified date: July 2008
• Source: Medical University of Vienna
• Contact: n/a
• Is FDA regulated: No
• Health authority: Austria: Agency for Health and Food Safety
• Study type: Interventional

Clinical Trial 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.

Recruitment information / eligibility

• Status: Completed
• Enrollment: 12
• Est. completion date: May 2003
• Est. primary completion date: May 2003
• Accepts healthy volunteers: Accepts Healthy Volunteers
• Gender: Male
• Age group: 19 Years to 35 Years

Eligibility

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

Allocation: Randomized, Endpoint Classification: Safety/Efficacy Study, Intervention Model: Crossover Assignment, Masking: Double Blind (Subject, Investigator), Primary Purpose: Diagnostic

Related Conditions & MeSH terms

• Ocular Physiology
• Regional Blood Flow

Intervention

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
• 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

Locations

Country	Name	City	State
Austria	Department of Clinical Pharmacology	Vienna

Sponsors (1)

Lead Sponsor	Collaborator
Medical University of Vienna

Country where clinical trial is conducted

Austria, 

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	Retinal arterial and venous diameter (Zeiss retinal vessel analyzer)		in total 6 hours	No
Primary	Retinal blood flow velocity (laser Doppler velocimetry)		in total 6 hours	No
Primary	Intraocular pressure (applanation tonometry)		in total 10 minutes	No