Table 1. Classification of clinical trials.

Stage	Primary goal	No. of subjects
Preclinical	Analysis in non-human subjects, to preliminary evaluate efficacy, toxicity and pharmacokinetics	–
Phase 0	Preliminary evaluation of efficacy, effectiveness and safety in healthy volunteers	10–20
Phase I	Preliminary evaluation of efficacy, effectiveness and safety in healthy volunteers	20–100
Phase II	Evaluation of efficacy, effectiveness and safety in patients	100–300
Phase III	Evaluation of efficacy, effectiveness and safety in patients	>300
Phase IV	Postmarketing surveillance	All subjects