This trial is active, not recruiting.

Condition erectile dysfunction
Treatments sildenafil, tadalafil, placebo
Sponsor University of Cambridge
Start date August 2006
Trial size 12 participants
Trial identifier NCT00463957, REC 06/Q0108/200


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.

United States No locations recruiting
Other Countries No locations recruiting

Study Design

Allocation randomized
Endpoint classification pharmacodynamics study
Intervention model parallel assignment
Masking double-blind
Primary purpose diagnostic

Primary Outcomes

visual persistence
time frame:
reaction time
time frame:

Eligibility Criteria

Male participants from 18 years up to 55 years old.

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

Additional Information

Official title The Pharmacological Basis for the Increase in Visual Time Constants Induced by Single Oral Doses of Sildenafil
Principal investigator Morris J Brown
Trial information was received from ClinicalTrials.gov and was last updated in January 2010.
Information provided to ClinicalTrials.gov by University of Cambridge.