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.
Aperçu de l'étude
Statut
Les conditions
Type d'étude
Inscription (Réel)
Phase
- N'est pas applicable
Contacts et emplacements
Lieux d'étude
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Vienna, L'Autriche, 1090
- Department of Clinical Pharmacology
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Critères de participation
Critère d'éligibilité
Âges éligibles pour étudier
Accepte les volontaires sains
Sexes éligibles pour l'étude
La description
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
Plan d'étude
Comment l'étude est-elle conçue ?
Détails de conception
- Objectif principal: Diagnostique
- Répartition: Randomisé
- Modèle interventionnel: Affectation croisée
- Masquage: Double
Armes et Interventions
Groupe de participants / Bras |
Intervention / Traitement |
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Comparateur placebo: 2
Placebo
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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
Substance: Physiologic saline solution 0.9% (placebo) Dosage form: i.v.
Dosage: 24ml/min over 64 min
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Comparateur actif: 1
vitamin C (Mayrhofer)
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Substance: Ascorbic acid (Mayrhofer) Manufacturer: Mayrhofer, Linz, Austria Dosage form: i.v.
Dosage: 24mg/min over 64 min Dosage reference: Ting HH 1996
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 |
Que mesure l'étude ?
Principaux critères de jugement
Mesure des résultats |
Délai |
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Retinal arterial and venous diameter (Zeiss retinal vessel analyzer)
Délai: in total 6 hours
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in total 6 hours
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Retinal blood flow velocity (laser Doppler velocimetry)
Délai: in total 6 hours
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in total 6 hours
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Intraocular pressure (applanation tonometry)
Délai: in total 10 minutes
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in total 10 minutes
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Collaborateurs et enquêteurs
Parrainer
Dates d'enregistrement des études
Dates principales de l'étude
Début de l'étude
Achèvement primaire (Réel)
Achèvement de l'étude (Réel)
Dates d'inscription aux études
Première soumission
Première soumission répondant aux critères de contrôle qualité
Première publication (Estimation)
Mises à jour des dossiers d'étude
Dernière mise à jour publiée (Estimation)
Dernière mise à jour soumise répondant aux critères de contrôle qualité
Dernière vérification
Plus d'information
Termes liés à cette étude
Termes MeSH pertinents supplémentaires
Autres numéros d'identification d'étude
- OPHT-161202
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