Condition category
Eye Diseases
Date applied
28/09/2007
Date assigned
28/09/2007
Last edited
28/08/2008
Prospective/Retrospective
Retrospectively registered
Overall trial status
Completed
Recruitment status
No longer recruiting

Plain English Summary

Not provided at time of registration

Trial website

Contact information

Type

Scientific

Primary contact

Prof Morris J Brown

ORCID ID

Contact details

Professor of Clinical Pharmacology
Department of Clinical Pharmacology
Level 6
ACCI
Box 110
Addenbrooke's Hospital
Cambridge
CB2 2QQ
United Kingdom
+44 01223 762574
mjb14@medschl.cam.ac.uk

Additional identifiers

EudraCT number

ClinicalTrials.gov number

Protocol/serial number

N0544183630

Study information

Scientific title

Acronym

Study hypothesis

Is the reason that sildenafil (Viagra) causes an increase in the time that the back of the eye perceives a visual image caused by the drug inhibiting phosphodiesterase type 6 (PDE6) in the light receptors in the eye?

Ethics approval

Not provided at time of registration

Study design

Randomised controlled trial

Primary study design

Interventional

Secondary study design

Randomised controlled trial

Trial setting

Hospitals

Trial type

Treatment

Patient information sheet

Condition

Eye Diseases: Visual sense

Intervention

Sildenafil (Viagra) and similar drugs eg tadalafil are phosphodiesterase type 5 inhibitor drugs that have been widely used in the treatment of erectile dysfunction in humans. One of the possible side effects of sildenafil is changes in vision and previous studies have shown that sildenafil can increase visual time constants ie cause a small increase in the length of time that an image is perceived on the back of the eye (retina). This can lead to symptoms of changes in vision for the patient taking the drug.
It has been suggested that the change in vision caused by sildenafil may be due to inhibition of the phosphodiesterase type 6 (PDE6) receptor in the light receptor cells of the eye. Although sildenafil and tadalafil predominantly act to inhibit the PDE5 receptor, sildenafil also has a significant degree of action in inhibiting the PDE6 receptor, whereas tadalafil shows very limited inhibition of this receptor.
We hope to establish whether PDE6 inhibition is the mechanism of the increase in visual time constants caused by sildenafil by performing a series of computerised visual tests to measure visual time constants following dosing with single oral doses of sildenafil, tadalafil or placebo. If PDE6 inhibition is the mechanism of the increase in visual time constants, we should observe changes in the visual time constants with sildenafil, but not tadalafil or placebo.
12 healthy male volunteers aged 18-55 years will be recruited to take part in this study. Volunteers will attend for a screening visit at which written informed consent will be taken and inclusion and exclusion criteria will be checked. A brief medical history will be taken, blood pressure measured and 12-lead electrocardiogram (heart tracing) performed. Vision will be tested to exclude colour blindness and a 20ml sample of venous blood will be taken for DNA analysis to look at differences in the PDE6 gene.

Intervention type

Drug

Phase

Not Specified

Drug names

sildenafil

Primary outcome measures

Effects of the drugs on retinal time constants (visual persistence and reaction times)

Secondary outcome measures

1. Effects of drugs on retinal time constants in different types of photoreceptors
2. Effect of PDE6 genotype on drug effects on retinal time constants

Overall trial start date

24/06/2006

Overall trial end date

30/06/2007

Reason abandoned

Eligibility

Participant inclusion criteria

Healthy male subjects aged 18-55 years. We have decided to only recruit male volunteers because phosphodiesterase inhibitors such as sildenafil and tadalafil are almost exclusively used in male patients.

Participant type

Patient

Age group

Adult

Gender

Male

Target number of participants

12 healthy volunteers

Participant exclusion criteria

1. Volunteers suffering from any significant medical or psychiatric illness. Subjects may be enrolled at the discretion of the principal investigator or his designated deputy if the illness would not affect the validity of the study or pose an added risk to the subject (e.g. mild asthma, hay fever). Specific conditions that will exclude volunteers from taking part are as follows:
1.1 Cardiac disease
1.2 Blood pressure <90/50mmHg or >160/100mmHg on screening visit
1.3 Renal disease
1.4 Liver disease
1.5 Stroke
1.6 Sickle cell anaemia
1.7 Multiple myeloma
1.8 Leukaemia
1.9 Bleeding disorders
1.10 Peyronie's disease
1.11 Priapism
2. Subjects receiving prescribed medications. Subjects may be included if the medication prescribed would not be considered to affect the validity of the study or pose an added risk to the study subject (e.g. inhaled asthma therapy). Specific exclusions include the following (due to interaction with the study drugs): nitrates, nicorandil, alpha blockers, erythromycin, cimetidine, rifampicin, phenytoin, carbamazepine, Phenobarbital, ritonavir, saquinavir, ketoconazole, itraconazole.
3. Female subjects
4. Subjects with known visual abnormalities other than refractive errors, including specifically: retinitis pigmentosa, optic neuropathy

Recruitment start date

24/06/2006

Recruitment end date

30/06/2007

Locations

Countries of recruitment

United Kingdom

Trial participating centre

Professor of Clinical Pharmacology
Cambridge
CB2 2QQ
United Kingdom

Sponsor information

Organisation

Record Provided by the NHSTCT Register - 2007 Update - Department of Health

Sponsor details

The Department of Health
Richmond House
79 Whitehall
London
SW1A 2NL
United Kingdom
+44 (0)20 7307 2622
dhmail@doh.gsi.org.uk

Sponsor type

Government

Website

http://www.dh.gov.uk/Home/fs/en

Funders

Funder type

Government

Funder name

Cambridge Consortium - Addenbrooke's (UK), Own Account NHS R&D Support Funding

Alternative name(s)

Funding Body Type

Funding Body Subtype

Location

Results and Publications

Publication and dissemination plan

Not provided at time of registration

Intention to publish date

Participant level data

Not provided at time of registration

Results - basic reporting

Publication summary

No planned publication

Publication citations

Additional files

Editorial Notes