Erectile Dysfunction
Conditions
Keywords
sildenafil, tadalafil, phosphodiesterase, visual persistence, reaction time
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.
Interventions
DRUGsildenafil
DRUGtadalafil
DRUGplacebo
Sponsors
University of Cambridge
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
DIAGNOSTIC
Masking
DOUBLE
Eligibility
Sex/Gender
MALE
Age
18 Years to 55 Years
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
Design outcomes
Primary
| Measure | Time frame |
|---|---|
| visual persistence | — |
| reaction time | — |
Countries
United Kingdom
Outcome results
None listed