When a new medicine is first developed, it is made in only small amounts in the laboratory. This supply is enough for the initial in vitro investigations and evaluations. If it proves to be successful, greater quantities are needed to meet the demands of the clinical trials and patients.

The chemical process used to produce Viagra™ is very complex. Picture 16 shows the steps that researchers had to go through to make Viagra™ when it was being developed for clinical use. A more efficient method was needed if it was ever going to be made in the large quantities needed to be a successful treatment for erectile dysfunction.

The research method involved the synthesis of many smaller molecules that were gradually built up and joined together to produce the Viagra™ molecule. This required many stages of synthesis and purification. It was not efficient enough for the amounts of Viagra™ needed for large-scale clinical trials and use with patients.

The production method builds up the Viagra™ from different starting molecules, which means that the reactions are more efficient and produce a lot less wastes. Chemists and chemical engineers are constantly improving this process to increase productivity and continue the reduction in wastes.

Making Viagra™ for the first time took a series of 11 reactions. It was not very efficient and to make 1 kg of Viagra™ required 23.8 kg of reagents and produced 139 litres of organic waste.

A more efficient method needed to be found to produce the larger quantities needed for trials and patients.

In 1990, 1 kg of Viagra™ was made. When it was launched, in 1998, 1 kg of Viagra™ was enough to supply the world's demand for just 10 minutes. Currently, the total demand from patients is 45 tonnes of very high quality Viagra™ every year.

After the discovery of a new medicine, sufficient quantities need to be made for clinical trials. The first stage is to scale-up the production. Picture 18 shows a laboratory that produces kilograms of the new medicines. This also helps to indicate what problems may be encountered as the medicine moves into full production.

There are over 45 tonnes of Viagra™ produced each year. Large reaction vessels, monitored and controlled by computers, ensure that large quantities of pure compound can be made to meet the demand. Picture 19 shows the top of a reaction vessel. Pipes feed reagents into the vessel and allow the harvesting of products. To the left is the control panel that monitors the process and allows the operator to make any necessary adjustments. Note how clean and tidy the area is. The highest standards of hygiene are required to produce pharmaceuticals.