HOW MEDICINES ARE LICENSED

• Initial research on new compounds is carried out in the laboratory.
• Promising compounds are then studied in animals, to investigate effects that cannot currently be predicted from the computer and test tube studies.
• Four phases of clinical assessment in humans follow strict guidelines.
• Phase I : a small number of healthy volunteers receives the compound. These trials will determine some aspects of how it works in humans and help to establish the dose required.
• Phase II : a group of, say, 100 to 200 patients with the condition are given the medicine to assess both that it works and that it does not produce unacceptable side-effects.
• Phase III : many more patients, perhaps 1,000 to 3,000, take the medicine under supervision for an appropriate period.
• If the results prove satisfactory in terms of quality, efficacy and safety, the data gathered are presented to the Licensing Authorities. If the Authorities are satisfied by the evidence, a licence is issued.
• Phase IV studies, involving thousands of patients, are initiated after the medicine has been made available for doctors to prescribe, and help to identify quickly any previously unforeseen side-effects.