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

Information source: Medical University of Vienna
ClinicalTrials.gov processed this data on August 23, 2015
Link to the current ClinicalTrials.gov record.

Condition(s) targeted: Ocular Physiology; Regional Blood Flow

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

Phase: N/A

Status: Completed

Sponsored by: Medical University of Vienna

Official(s) and/or principal investigator(s):
Gabriele Fuchsjäger-Mayrl, M.D., Principal Investigator, Affiliation: Department of Clinical Pharmacology, Medical University of Vienna


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.

Clinical Details

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

Study design: Allocation: Randomized, Endpoint Classification: Safety/Efficacy Study, Intervention Model: Crossover Assignment, Masking: Double Blind (Subject, Investigator), Primary Purpose: Treatment

Primary outcome: Choroidal pressure-blood flow relationship


Minimum age: 19 Years. Maximum age: 35 Years. Gender(s): Male.


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


- 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

Locations and Contacts

Department of Clinical Pharmacology, Vienna 1090, Austria
Additional Information

Starting date: August 2005
Last updated: July 8, 2008

Page last updated: August 23, 2015

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