Ocular PhysiologyNCT00712907
Effects of Vitamin C on Hyperoxia-Induced Reduction of Retinal Blood Flow
A study testing vitamin C (Mayrhofer) 24mg/min i.v. for 64 min and 100% O2 (AGA) two times for 12 min in people with Ocular Physiology and Regional Blood Flow, run by Medical University of Vienna at 1 site in Austria.
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. Read more about this study
- Who is it for?
- Ages 19 to 35 years, men onlyHealthy volunteers can take part
- Conditions the study is for
- Ocular Physiology, Regional Blood Flow
- What is being tested?
- vitamin C (Mayrhofer) 24mg/min i.v. for 64 min and 100% O2 (AGA) two times for 12 min
- Type of treatment
- Injection or infusion
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 12 participants
- Where
- 1 siteAustria
- Study dates
- Feb 2003to May 2003
- Phase
- Interventional
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 19 to 35 years
- Men only
- Healthy volunteers accepted
- Adult
Who may be able to join
- 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.
Who cannot join
- 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
Trial locations and contacts
1 site in 1 country.
Austria1 site
Department of Clinical Pharmacology
Vienna, State of Vienna, 1090
About this study
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.
- Conditions
- Ocular Physiology, Regional Blood Flow
- Being tested
- vitamin C (Mayrhofer) 24mg/min i.v. for 64 min, Placebo, 100% O2 (AGA) two times for 12 min
- Keywords
- vitamin C, retinal blood flow, intraocular pressure, retinal vessel diameter
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
vitamin C (Mayrhofer) 24mg/min i.v. for 64 minDietary supplement
Substance: Ascorbic acid (Mayrhofer) Manufacturer: Mayrhofer, Linz, Austria Dosage form: i.v. Dosage: 24mg/min over 64 min Dosage reference: Ting HH 1996
PlaceboDietary 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 minOther
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
| Study group | Role | What they receive |
|---|---|---|
| 1 | Active comparator | vitamin C (Mayrhofer) Receives: Dietary Supplement: vitamin C (Mayrhofer) 24mg/min i.v. for 64 min; Other: 100% O2 (AGA) two times for 12 min |
| 2 | Placebo comparator | Placebo Receives: Dietary Supplement: Placebo; Other: 100% O2 (AGA) two times for 12 min |
What is being measured
The primary outcome is the main question the study is designed to answer.
Retinal arterial and venous diameter (Zeiss retinal vessel analyzer)
Measured: in total 6 hours
Retinal blood flow velocity (laser Doppler velocimetry)
Measured: in total 6 hours
Intraocular pressure (applanation tonometry)
Measured: in total 10 minutes
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted10 Jul 2008 (estimated)
- Study startFeb 2003
- Primary completionMay 2003
- Study completionMay 2003
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Ocular PhysiologyStudies of the same condition, open and under way.
- More trials run by Medical University of ViennaThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Diagnosis
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Double blind
- Who is masked
- Participant, Investigator
- Enrolment
- 12 participants (actual)
Sponsor and investigators
- Lead sponsor
- Medical University of Vienna
- Sponsor type
- University, hospital or other
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT00712907
- Sponsor's protocol ID
- OPHT-161202
- Status last verified
- Jul 2008
- First submitted
- 8 Jul 2008
- Last updated
- 10 Jul 2008
- Results posted
- No
- Data monitoring committee
- Yes
Study at a glance
From the registry record, last updated by the sponsor on 10 Jul 2008. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Effects of Vitamin C on Hyperoxia-Induced Reduction of Retinal Blood Flow
- ClinicalTrials.gov ID
- NCT00712907
- Acronym / sponsor ID
- OPHT-161202
- Conditions
- Ocular Physiology, Regional Blood Flow
- Keywords
- vitamin C, retinal blood flow, intraocular pressure, retinal vessel diameter
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 12 participants (actual)
- Lead sponsor
- Medical University of ViennaUniversity, hospital or other
- Study start
- Feb 2003
- Primary completion
- May 2003 (actual)
- Study completion
- May 2003 (actual)
- First posted
- 10 Jul 2008 (estimated)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
Study design
- Primary purpose
- Diagnosis
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Double blind (participant, investigator)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| 1 | Active comparator | Dietary Supplement: vitamin C (Mayrhofer) 24mg/min i.v. for 64 min, Other: 100% O2 (AGA) two times for 12 minvitamin C (Mayrhofer) |
| 2 | Placebo comparator | Dietary Supplement: Placebo, Other: 100% O2 (AGA) two times for 12 minPlacebo |
Who may qualify
- Ages
- 19 to 35 years
- Sex
- Male only
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (5 listed)
- 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.
Key exclusion criteria (6 listed)
- 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
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| vitamin C (Mayrhofer) 24mg/min i.v. for 64 minSubstance: Ascorbic acid (Mayrhofer) Manufacturer: Mayrhofer, Linz, Austria Dosage form: i.v. Dosage: 24mg/min over 64 min Dosage reference: Ting HH 1996 | Dietary supplement | 1 |
| PlaceboSubstance: Physiologic saline solution 0.9% (placebo) Dosage form: i.v. Dosage: 24ml/min over 64 min | Dietary supplement | 2 |
| 100% O2 (AGA) two times for 12 minSubstance: 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 | Other | 1, 2 |
Primary outcome
Retinal arterial and venous diameter (Zeiss retinal vessel analyzer)
Time frame: in total 6 hours
Retinal blood flow velocity (laser Doppler velocimetry)
Time frame: in total 6 hours
Intraocular pressure (applanation tonometry)
Time frame: in total 10 minutes
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 10 Jul 2008.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
The record lists no contact. Use the official record to reach the sponsor.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing vitamin C (Mayrhofer) 24mg/min i.v. for 64 min and 100% O2 (AGA) two times for 12 min in people with Ocular Physiology and Regional Blood Flow, run by Medical University of Vienna at 1 site in Austria.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 5 inclusion and 6 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 10 Jul 2008. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Austria. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Retinal arterial and venous diameter (Zeiss retinal vessel analyzer) (time frame: in total 6 hours). The study lists 3 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 10 Jul 2008.