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

• Sponsor: Medical University of Vienna (Other)
• Overall Status: Completed
• CT.gov ID: NCT00280462
• Collaborator: (none)
• Enrollment: 21
• Location: 1
• Arms: 3
• Duration (Months): 8
• Patients Per Site Per Month: 2.6

Study Details

Study Description

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.

Condition or Disease	Intervention/Treatment	Phase
Ocular Physiology; Regional Blood Flow	Drug: Nifedipine (drug); Drug: L-Arginin (drug); Drug: Placebo	N/A

Study Design

• Study Type: Interventional
• Actual Enrollment: 21 participants
• Allocation: Randomized
• Intervention Model: Crossover Assignment
• Masking: Double (Participant, Investigator)
• Primary Purpose: Treatment
• Official Title: Choroidal Blood Flow Regulation During Isometric Exercise: Effects of Ca2+-Channel Blockade
• Study Start Date: Aug 1, 2005
• Actual Primary Completion Date: Apr 1, 2006
• Actual Study Completion Date: Apr 1, 2006

Arms and Interventions

Arm	Intervention/Treatment
Active Comparator: 1 Nifedipine	Drug: 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; Drug: L-Arginin (drug); L-Arginin (Clinalfa AG, Läufelfingen, Switzerland) 30% sodium chlorid solution, dose: 1g/min over 30 minutes; Drug: Placebo; Placebo
Active Comparator: 2 L-Arginin	Drug: 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; Drug: L-Arginin (drug); L-Arginin (Clinalfa AG, Läufelfingen, Switzerland) 30% sodium chlorid solution, dose: 1g/min over 30 minutes; Drug: Placebo; Placebo
Placebo Comparator: 3 Placebo	Drug: 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; Drug: L-Arginin (drug); L-Arginin (Clinalfa AG, Läufelfingen, Switzerland) 30% sodium chlorid solution, dose: 1g/min over 30 minutes; Drug: Placebo; Placebo

Outcome Measures

Primary Outcome Measures

1. Choroidal pressure-blood flow relationship [in total 3x 3 hours]

Eligibility Criteria

Criteria

• Ages Eligible for Study: 19 Years to 35 Years
• Sexes Eligible for Study: Male
• Accepts Healthy Volunteers: Yes

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

Contacts and Locations

Locations

	Site	City	State	Country	Postal Code
1	Department of Clinical Pharmacology	Vienna		Austria	1090

Sponsors and Collaborators

• Medical University of Vienna

Investigators

• Principal Investigator: Gabriele Fuchsjäger-Mayrl, M.D., Department of Clinical Pharmacology, Medical University of Vienna

Study Documents (Full-Text)

None provided.

More Information

Publications

None provided.

• ClinicalTrials.gov Identifier: NCT00280462
• Other Study ID Numbers: OPHT-110705
• First Posted: Jan 23, 2006
• Last Update Posted: Jul 9, 2008
• Last Verified: Jul 1, 2008

• Keywords provided by , ,: Nifedipine; Choroidal blood flow; Choroidal autoregulation; Isometric exercise
• Additional relevant MeSH terms: Nifedipine

Study Results

No Results Posted as of Jul 9, 2008