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

NCT00280462 | Completed DMC

• 1 other identifier: OPHT-110705
• Study Type: interventional
• Target: 21
• Locations: 1 country
• Sites: 1

Brief Summary

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.

Conditions

Ocular Physiology; Regional Blood Flow

Keywords

Nifedipine; Choroidal blood flow; Choroidal autoregulation; Isometric exercise

Outcome Measures

Primary Outcomes (1)

• Choroidal pressure-blood flow relationship

  in total 3x 3 hours

Study Arms (3)

1

ACTIVE COMPARATOR

Nifedipine

Drug: Nifedipine (drug); Drug: L-Arginin (drug); Drug: Placebo

2

ACTIVE COMPARATOR

L-Arginin

Drug: Nifedipine (drug); Drug: L-Arginin (drug); Drug: Placebo

3

PLACEBO COMPARATOR

Placebo

Drug: Nifedipine (drug); Drug: L-Arginin (drug); Drug: Placebo

Interventions

Nifedipine (drug) 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

1; 2; 3

L-Arginin (drug) DRUG

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

1; 2; 3

Placebo DRUG

Placebo

1; 2; 3

Eligibility Criteria

• Age: 19 Years - 35 Years
• Sex: male
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• 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.

You may not qualify if:

• 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

Sponsors & Collaborators

• Medical University of Vienna: lead

Study Sites (1)

Department of Clinical Pharmacology

Vienna, 1090, Austria

Location

Related Publications (1)

• 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.

  PMID: 22199246 DERIVED

MeSH Terms

Interventions

Nifedipine; Pharmaceutical Preparations; Arginine

Intervention Hierarchy (Ancestors)

Dihydropyridines; Pyridines; Heterocyclic Compounds, 1-Ring; Heterocyclic Compounds; Amino Acids, Basic; Amino Acids; Amino Acids, Peptides, and Proteins; Amino Acids, Diamino; Amino Acids, Essential

Study Officials

• Gabriele Fuchsjäger-Mayrl, M.D.

  Department of Clinical Pharmacology, Medical University of Vienna

  PRINCIPAL INVESTIGATOR

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: DOUBLE
• Who Masked: PARTICIPANT, INVESTIGATOR
• Purpose: TREATMENT
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER

Study Record Dates

• First Submitted: January 19, 2006
• First Posted: January 23, 2006
• Study Start: August 1, 2005
• Primary Completion: April 1, 2006
• Study Completion: April 1, 2006
• Last Updated: July 9, 2008

Record last verified: 2008-07

Locations

AU (1)