Official Title: “Effects of Topical Clonidine vs. Brimonidine on Choroidal Blood Flow and Intraocular Pressure During Isometric Exercise”

Brimonidine tartrate is an alpha-2 agonist ocular hypotensive drug that exerts its effect by causing both a decrease in aqueous production and an increase in uveoscleral outflow. It has been proven to reduce increased intraocular pressure in glaucoma and ocular hypertension. As an alpha 2 agonist Brimonidine belongs to the same class of drugs as Clonidine; however, its molecular structure is sufficiently different to make it more selective for the alpha 2 receptor than Clonidine. Unlike Clonidine, Brimonidine does not appear to have an effect on the central nervous system and therefore does not cause sedation or systemic hypotension.

In addition to their known effect of lowering intraocular pressure, alpha 2 adrenoceptor agonists are neuroprotective. It has, however, been shown that Brimonidine is a very potent vasoconstrictor in the ciliary body thus reducing aqueous humor production. Little is, however, known about potential vasoconstrictor effects of Brimonidine in the posterior pole of the eye. This is of clinical importance, because optic nerve head ischemia appears to contribute to glaucoma pathophysiology.

This study is performed to investigate the effects of topical Clonidine vs. topical Brimonidine on choroidal blood flow and intraocular pressure during isometric exercise.

Study Type: Interventional

Study Design: Treatment, Randomized, Double-Blind, Active Control, Crossover Assignment, Safety/Efficacy Study

Intervention(s) in this Clinical Trial

• Drug: Clonidin
• Drug: Brimonidine

Primary Measures

• Choroidal pressure-flow relationship

Inclusion Criteria:

• Men aged between 19 and 35 years, nonsmokers
• Body mass index between 15th and 85th percentile (Must A et al. 1991)
• Normal findings in the medical history and physical examination unless the investigator considers an abnormality to be clinically irrelevant
• Normal ophthalmic findings, ametropy < 3 Dpt.
• Intraocular pressure between 10 and 18 mmHg.

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
• History or family history of epilepsy

Gender Eligibility for this Clinical Trial: Male

Minimum Age for this Clinical Trial: 19 Years

Maximum Age for this Clinical Trial: 35 Years

Are Healthy Volunteers Accepted for this Clinical Trial?: Accepts Healthy Volunteers

Lead Sponsor: Medical University of Vienna

Overall Clinical Trial Officials and Contacts

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

Information obtained from ClinicalTrials.gov on September 05, 2008

Link to the current ClinicalTrials.gov record. http://clinicaltrials.gov/show/NCT00312416

Study ID Number: OPHT-121203B

ClinicalTrials.gov Identifier: NCT00312416

Health Authority: Austria: Federal Ministry for Health and Women