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The Pharmacological Basis for the Increase in Visual Time Constants Induced by Single Oral Doses of Sildenafil

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ClinicalTrials.gov Identifier: NCT00463957
Recruitment Status : Unknown
Verified April 2007 by University of Cambridge.
Recruitment status was:  Active, not recruiting
First Posted : April 20, 2007
Last Update Posted : January 12, 2010
Information provided by:
University of Cambridge

Brief Summary:
Sildenafil and similar drugs have been used for several years to treat erectile dysfunction. It has been noticed that in some people, sildenafil causes a subtle increase in the length of time that visual images that we see are retained by the retina. It is thought that this might be due to an effect of sildenafil on inhibiting an enzyme called phosphodiesterase type 6 (PDE6) which is present in the retina. By giving single oral doses of sildenafil and a similar drug called tadalafil which has less effect on PDE6, we hypothesise that this is the mechanism of the change in vision caused by sildenafil. By performing computerised visual test, we plan to compare the effects of sildenafil, tadalafil and placebo tablets on vision in healthy volunteers.

Condition or disease Intervention/treatment
Erectile Dysfunction Drug: sildenafil Drug: tadalafil Drug: placebo

Study Type : Interventional  (Clinical Trial)
Estimated Enrollment : 12 participants
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double
Primary Purpose: Diagnostic
Official Title: The Pharmacological Basis for the Increase in Visual Time Constants Induced by Single Oral Doses of Sildenafil
Study Start Date : August 2006

Resource links provided by the National Library of Medicine

U.S. FDA Resources

Primary Outcome Measures :
  1. visual persistence
  2. reaction time

Information from the National Library of Medicine

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Ages Eligible for Study:   18 Years to 55 Years   (Adult)
Sexes Eligible for Study:   Male
Accepts Healthy Volunteers:   Yes

Inclusion Criteria:

  • Healthy
  • Male
  • 18-55 years

Exclusion Criteria:

  • Significant medical or psychiatric illness
  • Cardiac disease
  • Hyper or hypotension
  • Renal disease
  • Liver disease
  • Stroke
  • Sickle cell anaemia
  • Multiple myeloma
  • Leukaemia
  • Bleeding disorders
  • Peyronie's disease
  • Priapism
  • Subjects receiving prescribed medications
  • Subjects with known visual abnormalities other than refractive errors, including retinitis pigmentosa, optic neuropathy

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT00463957

United Kingdom
University of Cambridge
Cambridge, United Kingdom
Sponsors and Collaborators
University of Cambridge
Principal Investigator: Morris J Brown University of Cambridge

ClinicalTrials.gov Identifier: NCT00463957     History of Changes
Other Study ID Numbers: REC 06/Q0108/200
First Posted: April 20, 2007    Key Record Dates
Last Update Posted: January 12, 2010
Last Verified: April 2007

Keywords provided by University of Cambridge:
visual persistence
reaction time

Additional relevant MeSH terms:
Erectile Dysfunction
Sexual Dysfunction, Physiological
Genital Diseases, Male
Sexual Dysfunctions, Psychological
Mental Disorders
Sildenafil Citrate
Vasodilator Agents
Phosphodiesterase 5 Inhibitors
Phosphodiesterase Inhibitors
Enzyme Inhibitors
Molecular Mechanisms of Pharmacological Action
Urological Agents