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Choroidal Blood Flow Regulation During Isometric Exercise: Effects of Ca2+-Channel Blockade

NCT ID: NCT00280462

Last Updated: 2008-07-09

Study Results

Results pending

The study team has not published outcome measurements, participant flow, or safety data for this trial yet. Check back later for updates.

Basic Information

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Recruitment Status

COMPLETED

Clinical Phase

NA

Total Enrollment

21 participants

Study Classification

INTERVENTIONAL

Study Start Date

2005-08-31

Study Completion Date

2006-04-30

Brief Summary

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Autoregulation is the ability of a vascular bed to maintain blood flow despite changes in perfusion pressure. For a long time it had been assumed that the choroid is a strictly passive vascular bed, which shows no autoregulation. However, recently several groups have identified some autoregulatory capacity of the human choroid. In the brain and the retina the mechanism behind autoregulation is most likely linked to changes in transmural pressure. In this model arterioles change their vascular tone depending on the pressure inside the vessel and outside the vessel. In the choroid, several observations argue against a direct involvement of arterioles. In a previous project we were able to identify that the nitric oxide (NO) - system as well as the endothelin system are involved in choroidal blood flow regulation during isometric exercise.

In the present study autoregulation of the choroid during isometric exercise will be investigated and the pressure/flow relationships will be observed in the absence or presence of a calcium antagonist - nifedipine.

Detailed Description

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Conditions

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Ocular Physiology Regional Blood Flow

Keywords

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Nifedipine Choroidal blood flow Choroidal autoregulation Isometric exercise

Study Design

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Allocation Method

RANDOMIZED

Intervention Model

CROSSOVER

Primary Study Purpose

TREATMENT

Blinding Strategy

DOUBLE

Participants Investigators

Study Groups

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1

Nifedipine

Group Type ACTIVE_COMPARATOR

Nifedipine (drug)

Intervention Type DRUG

Nifedipine (Adalat®, Bayer, Leverkusen, Germany) dose: 15µg/kg bolus infusion over 5 minutes; 0.2 µg/(kg.min) maintenance dose infusion period 25 minutes

L-Arginin (drug)

Intervention Type DRUG

L-Arginin (Clinalfa AG, Läufelfingen, Switzerland) 30% sodium chlorid solution, dose: 1g/min over 30 minutes

Placebo

Intervention Type DRUG

Placebo

2

L-Arginin

Group Type ACTIVE_COMPARATOR

Nifedipine (drug)

Intervention Type DRUG

Nifedipine (Adalat®, Bayer, Leverkusen, Germany) dose: 15µg/kg bolus infusion over 5 minutes; 0.2 µg/(kg.min) maintenance dose infusion period 25 minutes

L-Arginin (drug)

Intervention Type DRUG

L-Arginin (Clinalfa AG, Läufelfingen, Switzerland) 30% sodium chlorid solution, dose: 1g/min over 30 minutes

Placebo

Intervention Type DRUG

Placebo

3

Placebo

Group Type PLACEBO_COMPARATOR

Nifedipine (drug)

Intervention Type DRUG

Nifedipine (Adalat®, Bayer, Leverkusen, Germany) dose: 15µg/kg bolus infusion over 5 minutes; 0.2 µg/(kg.min) maintenance dose infusion period 25 minutes

L-Arginin (drug)

Intervention Type DRUG

L-Arginin (Clinalfa AG, Läufelfingen, Switzerland) 30% sodium chlorid solution, dose: 1g/min over 30 minutes

Placebo

Intervention Type DRUG

Placebo

Interventions

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Nifedipine (drug)

Nifedipine (Adalat®, Bayer, Leverkusen, Germany) dose: 15µg/kg bolus infusion over 5 minutes; 0.2 µg/(kg.min) maintenance dose infusion period 25 minutes

Intervention Type DRUG

L-Arginin (drug)

L-Arginin (Clinalfa AG, Läufelfingen, Switzerland) 30% sodium chlorid solution, dose: 1g/min over 30 minutes

Intervention Type DRUG

Placebo

Placebo

Intervention Type DRUG

Eligibility Criteria

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Inclusion Criteria

* Men aged between 19 and 35 years, nonsmokers
* Body mass index between 15th and 85th percentile (Must et al. 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, ametropy more than 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
Minimum Eligible Age

19 Years

Maximum Eligible Age

35 Years

Eligible Sex

MALE

Accepts Healthy Volunteers

Yes

Sponsors

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Medical University of Vienna

OTHER

Sponsor Role lead

Responsible Party

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Department of Clinical Pharmacology, Medical University of Vienna

Principal Investigators

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Gabriele Fuchsjäger-Mayrl, M.D.

Role: PRINCIPAL_INVESTIGATOR

Department of Clinical Pharmacology, Medical University of Vienna

Locations

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Department of Clinical Pharmacology

Vienna, , Austria

Site Status

Countries

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Austria

References

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Schmidl D, Prinz A, Kolodjaschna J, Polska E, Luksch A, Fuchsjager-Mayrl G, Garhofer G, Schmetterer L. Effect of nifedipine on choroidal blood flow regulation during isometric exercise. Invest Ophthalmol Vis Sci. 2012 Jan 25;53(1):374-8. doi: 10.1167/iovs.11-8536.

Reference Type DERIVED
PMID: 22199246 (View on PubMed)

Other Identifiers

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OPHT-110705

Identifier Type: -

Identifier Source: org_study_id