How Viagra Was Discovered

How Viagra Was Discovered

Most people assume that the scientists who discovered Viagra had spent years searching for a cure for erectile dysfunction. In fact, the team at Pfizer were as surprised as anyone when their research on a potential treatment for heart disease revealed a side effect that sparked a sexual health revolution. Ian Osterloh, one of the main scientists working on the project has spoken about how Pfizer discovered sildenafil citrate, better known as Viagra, the world’s most famous treatment for erectile dysfunction or impotence.

Osterloh recalls that he first came across the project in the late 1980s, when he learned colleagues at Pfizer's laboratories in Sandwich, a small town on England's southeast coast, had come up with a theory about selectively blocking an enzyme called PDE5. They believed they might produce a drug to block PDE5 that could expand blood vessels and treat angina. By the early 1990’s, the team had discovered a powerful and selective inhibitor of PDE5, known at the time as UK-92480. Early tests showed it had a moderate effect on the blood vessels of healthy volunteers, which was a promising sign. However, the inhibitor only remained in the body for a relatively short time, and when taken three times a day — to maintain a constant effect — it gave some volunteers muscle aches.

In one of the studies undertaken, male volunteers also reported increased erections several days after the intial dose. Pfizer’s didn’t think much of this side effect at the time. Osterloh remembers thinking that even if it did work, who would want to take a drug on a Wednesday to get an erection on a Saturday? So they continued on with the angina studies. However, increased erections were now being reported in even more volunteer studies, so they decided to follow up on these reports to see where it would take them.

Coincidently, around the same time other studies were revealing more information about the biochemical pathway involved in the erection process. This helped with understanding how the drug might amplify the effects of sexual stimulation in opening up the blood vessels in the penis. With UK-92480's chances of treating angina now slim, they decided to run pilot studies in patients with erectile dysfunction (ED). In the initial study, the men watched erotic videos while a device monitored girth and hardness of their penises. The initial results were encouraging and showed the drug was much more effective than a placebo.

However, they still had a long way to go and many unanswered questions. Would the drug be effective when used in a less clinical setting and after a single dose? How could they measure its effects accurately without being intrusive? Would it work in men with ED caused by different medical conditions, such as high blood pressure, diabetes, heart disease or prostatectomy?

The next trial included more than 300 patients from the U.K., Sweden and France. They included men with diabetes, extended the treatment duration to four weeks and tested three different doses and a placebo. Some clinicians in the field doubted that an oral drug could selectively open up blood vessels in the penis, but they persevered

When the results finally came through they exceeded anyone’s wildest expectations. There was a very good dose-response correlation, with around 90 per cent of patients responding at the highest dose. The drug was also well tolerated, with very few patients reporting muscle aches and very few dropping out of the study. The diaries and questionnaires also provided accurate and consistent results.

The most expensive stage of drug development was next-long-term clinical trials of thousands of patients worldwide. This requires hundreds of millions of dollars — and still there is only a one-in-five chance of the drug passing these tests and gaining a license. In the mean-time, large numbers of impotence sufferers had written to Pfizer’s explaining how the condition was having devastating effects on their relationships and how desperate they were for effective treatment. According to Osterloh, these letters further convinced them there was a serious need for an ED treatment and encouraged Pfizer’s to keep pushing the program internally.

The project received the necessary extra funding and as the clinical program continued they found the results were better and better. The drug worked well in men with a variety of causes of ED, including diabetes and spinal cord injury. It also continued to be well tolerated.
In 1997, 12 years after the project had begun, eight years after the first synthesis of UK-92480 and four years after the first ED pilot study, Pfizer finally had enough information to apply for a licence from the regulatory authorities.

The rest, as they say, is history.

This information has been brought to you by Firstmed.co.uk, the leading erectile dysfunction clinic in the UK.
If you wish to discuss any of the above issues in more detail, do not hesitate to contact info@firstmed.co.uk or call +44 (0)870 199 5287

Firstmed is an online erectile dysfunction clinic in the UK and specialises in genuine, prescription Viagra , and other leading impotence treatment.