Clinical Trials

3. Classification


For commercial purposes, trials have been classified into various phases, determined by the pharmaceutical industry based on the four phases of development of a particular drug (Phases I–IV) (Chow & Liu, 1998).

Figure 1

Figure 1 depicts the four phases of developing a pharmaceutical drug, the length of time each phase takes and number of volunteers per phase including; Animal/Laboratory studies (4 ½ years), Phase I (15-30 volunteers) Phase II (fewer than 100 volunteers) Phase III (100s to 1000s volunteers) total about 8 ½ years, FDA approval (1 ½ years) and Phase IV (after approval).

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Phase I - Test Drug in Healthy Volunteers
Phase II - Test Drug in Patients with the Disease
Phase III - Test Drug Against Placebo or Standard Therapy
Phase IV - Test Drug While in the Marketplace
Chow SC, Liu JP. (1998). Design and analysis of clinical trials: Concept and methodologies. Chichester: John Wiley & Sons.