In the past, all medicines came from plants or animals. Although some important medicines still come from plants or animals (e.g. morphine), most medicines used today in the developed world are manufactured through chemical processes.

All new medicines must undergo thorough testing before being approved for use. Before a new medicine can be tried in humans it must undergo extensive testing in the laboratory, to assess its safety and biological activity. This 'pre-clinical' development stage may last as long as 3 or 4 years. Then clinical trials in human volunteers, determine if a medicine is safe and effective, at what doses it works best and what side effects it causes.

A typical clinical trial development programme

Only one or two of thousands of new chemical compounds evaluated ever gets as far as being approved for use on prescription by doctors. It costs in the region of US$800 million to develop a new medicine and can take 12 years to make a new medicine available for doctors to prescribe.

In 2002, AstraZeneca invested over US$3 billion on research and development to improve current treatments and develop new medicines for a wide range of illnesses.

Each new medicine entering development is given a chemical name (e.g. lisinopril, used to treat high blood pressure ). Occasionally, this chemical name is called something different in different countries (eg. paracetamol and acetaminophen are the same). However, once a medicine has been licensed for use in patients by the medicines agency of a country, the manufacturer can sell the medicine under a brand or trade name (eg Zestril).

Patenting of a new medicine guarantees the manufacturer a 20-year period of protection, during which no other companies can legally make or sell the medicine. However, once this period has expired, other pharmaceutical companies can make the medicine. These ‘copycat’ medicines are called ‘generic’ medicines.