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

University of Cambridge

Status

Unknown

Conditions

Erectile Dysfunction

Treatments

Drug: placebo

Drug: sildenafil

Drug: tadalafil

Study type

Interventional

Funder types

Other

Identifiers

NCT00463957

REC 06/Q0108/200

Details and patient eligibility

About

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.

Sex

Male

Ages

18 to 55 years old

Volunteers

Accepts Healthy Volunteers

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