Erectile dysfunction: the treatment of erectile dysfunction.

The science of curing erection problems

After the International Journal of Impotence Research (2002), volume 14, 226 - 245

Effective oral therapies for erectile dysfunction have caused significant changes in the design and conduct of clinical trials.

Instead of penile plethysmography or doppler ultra sonography, patient-based methods of erection assessment are needed.

More particularly, during the development of Viagra (sildenafil), the need for a good way of establishing  erectile and sexual dysfunction was recognized, which led to the development of the International Index of Erectile Function (IIED).

This was designed for use in multiple languages and cultures, and now adopted as the best treatment outcome measure for work on erectile dysfunction. The International Index of Erectile Function has had a major impact on the field of clinical trials around erectile dysfunction.

The International Index of Erectile Function is made up of a scale of 15 items divided into five areas of sexual function: erectile and orgasmic function, sexual desire, satisfaction with intercourse, and overall sexual satisfaction.

Two items from the area of erectile function are designed to look at components of erectile dysfunction: the ability to penetrate and the ability to remain erect.

Tests performed in various studies before the adoption of the International Index of Erectile Function in clinical trials included psychometric tests of reliability, sensitivity, and validity.

Scale reliability and internal consistency were also examined for each of the five domains and additionally for the total scale.

Discriminant validity was also checked, in a process which compared the responses of men with erectile dysfunction patients before their treatment with age-comparable controls who received no treatment.

Convergent validity was demonstrated by comparison of the men's International Index of Erectile Function scores with doctors' ratings of sexual function. Lastly, divergent validity was proven by comparing the scores from the International Index of Erectile Function with scores of other scales. 

Other pages on this website about the treatment of erectile dysfunction, erectile dysfunction and impotence

[ Home ] [ Diagnosis of Erectile Dysfunction ] [ The Causes of Erectile Dysfunction ] [ Effects of Erectile Dysfunction On Men and Their Partners ] [ Treatment for Erectile Dysfunction ] [ The Science of Treating Erectile Dysfunction ]

Other sections on the website about erectile dysfunction

[ Treatment of erectile dysfunction with drugs ] [ ED & cardiovascular disease ] [ The partner and ED ] [ Vascular disease and ED ]

The International Index of Erectile Function as a measure in Erectile Dysfunction trials

The International Index of Erectile Function was designed as a measure for use in clinical trials of erectile dysfunction. Because of its close involvement with the Viagra trial program, the assessment of its usefulness began with a review of published studies of Viagra in which the International Index of Erectile Function was used as a measure of effectiveness.

Questions 3 and 4 of the International Index of Erectile Function were used as endpoints in the first two large clinical trials of Viagra in the United States.

One of these studies, a fixed dose trial of over 530 men with erectile dysfunction, where for 6 months men received either placebo, or a fixed dose of Viagra, requested that men report their attempts at sexual activity, including whether or not they had satisfactory erections and whether they actually attempted to have intercourse.

Mean scores on question 3 (initial penetration) and question 4 (continued penetration) increased from 2.0 and 1.5 respectively at the start of the trial to 4.0 and 3.9 respectively at 100 mg dose. The scores for men given placebo were 2.2 and 2.1. These differences are all highly significant (P less than 0.001). Other questions revealed a similar pattern of results: 56, 77 and 84% of men on the doses of 25, 50 and 100 mg of Viagra reported improved erectile capacity.

In the first European trials on men with erectile dysfunction, questions 3 and 4 were also used as endpoints in the first two, large-scale randomized trials of Viagra. In one study, over 500 men with erectile dysfunction of various origins and etiologies were assigned at random to 3 months of treatment with placebo or treatment with a fixed dose of 25, 50 or 100 mg of Viagra.

After 3 months of treatment, mean scores on Q3 and Q4 increased respectively from 2.1 to 3.8 and 1.9 to 3.7 in the 100 mg Viagra group, compared with 2.1 and 2.0 for men treated with placebo. Similar results were obtained in the second study, which took place in Belgium, France, Germany, the Netherlands and the UK, in which trial 315 men with erectile dysfunction were randomly assigned to the test's various regimes.

Besides showing the effectiveness of treatment with sildenafil Viagra in various studies it was clear that the International Index of Erectile Function was consistent across different countries and tests.

Slightly higher post-treatment assessment scores were found in the two Asian studies, but the differences between the drug and the placebo on questions 3 and 4 and the erectile function questions were very similar to those recorded in the European and US studies.

International Index of Erectile Function scores with Viagra therapy

How does treatment with Viagra normalize erectile function as measured on the International Index of Erectile Function? In one study, a group of men without erectile dysfunction were compared with men with erectile dysfunction by a process involving randomly assigned  double-blind treatment with Viagra or a placebo.

The men's responses to the questions of the International Index of Erectile Function responses were compared both before and after treatment. Not surprisingly, for men who had received Viagra, mean scores on Question 3 increased from 1.7 before treatment to 3.6 at later follow-up, while Question 4 increased from 1.6 before treatment to 3.7 following treatment for the symptoms of erectile dysfunction.

The comparative scores for men without erectile dysfunction were 4.3 and 4.2. This means that Viagra restored erectile function in men with pre-existing erection problems to about 85% of the erectile capacity of men who did not have erectile dysfunction.

In passing, it is worth noting that men in the control group did not reach the maximum score possible - 5.0 - which means that there is a slight reduction of erectile capacity among men in the older age ranges.

Overall, when untreated age-matched controls are compared with treated men who had documented erectile dysfunction, the mean erectile function score following treatment was 25.8 for controls and 21.8 for men who had had erectile dysfunction.

The lower scores in the Viagra group may be in part the consequence of a small number of men who did not respond to treatment with Viagra, which means that the overall average score was lower than it would otherwise have been.

Four of the five areas which the International Index of Erectile Function was designed to measure - specifically erectile function, intercourse satisfaction, orgasmic function and overall satisfaction - were found to improve markedly following Viagra treatment.

As you may already know, Viagra is not an aphrodisiac, so it is not surprising that little change was noticed in the reporting of sexual desire.

 The evidence was that firstly, scores among the patient group about sexual desire were, broadly speaking, very similar to to the control group before treatment and secondly, Viagra acts on the peripheral mechanism of erection and has little or not effect on the central nervous system. This type of result has been seen many times, and in any event there is no study which has shown significant increases in sexual desire when men take Viagra.