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

The recruitment status of this study is unknown. The completion date has passed and the status has not been verified in more than two years.
Verified April 2007 by University of Cambridge.
Recruitment status was:  Active, not recruiting
Information provided by:
University of Cambridge Identifier:
First received: April 19, 2007
Last updated: January 11, 2010
Last verified: April 2007
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 Intervention
Erectile Dysfunction Drug: sildenafil Drug: tadalafil Drug: placebo

Study Type: Interventional
Study Design: 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

Resource links provided by NLM:

Further study details as provided by University of Cambridge:

Primary Outcome Measures:
  • visual persistence
  • reaction time

Estimated Enrollment: 12
Study Start Date: August 2006

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
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Please refer to this study by its identifier: NCT00463957

United Kingdom
University of Cambridge
Cambridge, United Kingdom
Sponsors and Collaborators
University of Cambridge
Principal Investigator: Morris J Brown University of Cambridge
  More Information Identifier: NCT00463957     History of Changes
Other Study ID Numbers: REC 06/Q0108/200
Study First Received: April 19, 2007
Last Updated: January 11, 2010

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 processed this record on August 18, 2017