Clinical trials internet resource
November 2004
Clinical trials process for drugs
Clinical trials for pharmaceutical products are carried out in four phases, only moving from one phase to the next if the previous phase has shown promising results. The four ‘ideal’ phases are as follows:
- Phase I – the drug is tested on a small number of healthy volunteers to test how it is metabolised, whether it is safe for humans and to find the best way of administering the treatment.
- Phase II – a small number of patients are given the drug to test for side effects, activity and optimum dose, and to start comparing it to the current treatment or a placebo.
- Phase III – the drug is given to a larger group of patients for continued testing of safety and efficacy and to compare it with the current treatment or a placebo. These trials are nearly always randomised.
- Phase IV – this phase occurs once the drug has been licensed and checks for possible long-term side effects of the drug. It is also known as post-marketing surveillance.