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Health, Sports & Psychology

The drug story: Viagra

Updated Tuesday, 9th September 2008

The Open Minds programme explores 'the drug story: Viagra'

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Viagra laboratory Copyrighted  image Icon Copyright: Production team

Pfizer sign Copyrighted  image Icon Copyright: Production team The US company Pfizer has been in Britain since the 1950s. It’s presence at Sandwich in Kent has gradually built up until today there are over 4,500 people employed in the research and manufacture of range of human and animal medicines.

It was here, back in 1985, that the company started work on what it hoped would be a new product to treat angina. They were aiming to come up with something that would relax vascular smooth tissue and increase blood flow in affected areas.

Altogether about 1,600 different compounds were produced during research, different molecules were tried until Pfizer came up with something called Sildenafil. But Trials aimed at obtaining a beneficial effect in the treatment of angina were disappointing, and in tests on healthy male volunteers doses were increased to see what would happen and what side effects would occur.

At high doses men reported headaches, visual disturbance, muscle ache and a change in erectile function. It was this latter phenomenon began to catch the scientists' attention and eventually led Pfizer to change direction and work towards producing a treatment for impotence or erectile dysfunction.

Male impotence is distressing to the sufferer and has been poorly understood by the general public. The emergence of Viagra has had the effect of bringing the subject out into the open and a study of the way the drug operates shows that impotence is not only caused by psychiatric disorders or breakdown of marriage but is, in many cases, caused by a deficient chemical reaction in the body which can be rectified by medical treatment.

Its estimated that about one in 10 men will experience significant erectile dysfunction problems during their life time and that the likelihood of problems will increase with age.

Ivan Jackson Copyrighted  image Icon Copyright: Production team Ivan Jackson, made his living as a hod carrier on a building site until one day he came home with aches and pains which he could not explain. After several visits to the doctor his condition was finally diagnosed as MS.

15 years later the disease affects him differently from week to week sometimes he has to use a wheel chair. MS made him impotent and he agreed to take part in blind testing of Viagra. Unknown to him he was first given the placebo or chalk tablets. He duly reported no effect. But later when he took Viagra the improvement he noted in erectile function was unmistakable.

In 1998 the new drug Sildenafil was produced under the brand name Viagra. It is the first oral treatment for erectile dysfunction and at the same time the first time the first drug to be rationed.

Viagra laboratory Copyrighted  image Icon Copyright: Production team

How Viagra works

When a man is sexually aroused, the brain sends a signal to nerve endings in the penis to release nitric oxide, this then acts via an enzyme to cause the creation of a chemical called cyclic Guanosine Monophospate or cGMP. It is this chemical that then relaxes the blood vessels in the penis allowing an erection to occur. However, at the same time as this is happening, another compound called phosphodiesterase operates to make cGMP inactive. In the healthy male the first process overwhelms the second and an erection can occur.

The problem that the man with erectile dysfunction has is that he cannot produce enough nitric oxide to allow the first process to dominate the second.

Viagra counters this by inhibiting the action of the phosphodiesterase – the second compound, so that even if not much cGMP is formed, it can still build up to a sufficient levels to allow an erection to occur.

open minds drug story viagra diagram inline Copyrighted  image Icon Copyright: Production team

For people like Ivan Jackson, the new drug has been a breakthrough. Options open to him before Viagra were complicated and unsubtle, often requiring him to have an erection whether it was convenient or not. Because Viagra only works when a man is sexually stimulated Ivan says it’s a big improvement on what went before.

Take it further

The Sexual Dysfunction Association

Interested in finding out more? See a collection of Open University science courses.





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