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  The Viagra™ story
            5. Trialling
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Clinical trials

Before a medicine is tried on people it undergoes many pre–clinical tests in the laboratory. These showed that Viagra™ was not toxic and could safely be used in clinical trials with healthy volunteers.

Trials

Trials are carefully planned to make certain that the results they produce are reliable. In double-blind, placebo controlled trials neither the doctors or their patients know if they are using the medicine or an inactive placebo. This prevents any bias in the experiment and also makes sure that any effects are down to the active ingredient and not just the patient feeling better because they are receiving a new type of treatment.

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Picture 21. Reported side effects of Viagra™.
Angina treatment

Even though a lot of time and money is invested in developing new medicines, many do not prove effective enough in clinical trials and never go into production. In 1991, trials looked at how effectively Viagra™ treated angina. Researchers wanted to see if it dilated the coronary arteries feeding the heart muscle and relieved the pain of angina. Results showed it would not be a good treatment for angina. However, some subjects reported some interesting side effects.

In small scale studies, some healthy volunteers reported that Viagra™ enhanced erections and so, in 1992, researchers changed direction and concentrated on developing Viagra™ as a treatment for erectile dysfunction.

Interactive graph
Picture 22. Trial results - effect of time on ability to get an erection. Roll over the image to see the effect of Viagra™.
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Picture 23. Results of trials with Viagra™.
Erectile dysfunction

Tests began in 1993 to see if Viagra™ could be used to treat erectile dysfunction. During the trials, Viagra™ was given to over 3,000 patients aged 19 to 87 years old. In 21 separate studies it proved to give statistically significant improvements when compared to the placebo.

During trials, researchers recorded the effect of Viagra™ on the ability of patients to maintain an erection. A tablet of Viagra™ was taken and its effects were measured an hour later. Patients also completed a questionnaire which gave information about the influence of Viagra™ on their ability to have intercourse.

Why is the placebo important?

A patient receiving a placebo would get a tablet that looked exactly the same as the tablet containing Viagra™. However, it would not contain any of the active ingredient. This takes account of the fact that some patients show an improvement simply by taking a tablet (even without an active ingredient). The control group gives an indication of how many people in the test group were probably responding to the tablet rather than the active ingredient.

Question 9
Look at the questions below. In each case, choose the best answer from the drop down list.

a) In a clinical trial, what is a placebo?

b) Why is a placebo necessary?

c) Why did some patients taking the placebo show an improvement in their erectile dysfunction?

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