[Drug research methodology: fundamentals].

The last few years have witnessed a veritable boom in the research and development of new drugs, as evidenced in the market by the introduction of sundry groups of medications against a wide variety of illnesses. Currently, between six and ten years of research are needed prior to the approval and sale of an investigational drug. During this time, the medication under study must go through different stages of investigation; the first of these is the preclinical assessment stage, followed by stages I, II and III of clinical assessment, and ending with stage IV of post commercialization clinical assessment. Drug research requires that all medications under study first be tested on laboratory animals (preclinical phase) prior to being tested on humans (the clinical phase). This latter phase, however, can proceed only once the drug has been shown to have potential therapeutic benefits, and, principally, no evidence of significant toxicity in animal testing. The subsequent assessment of the drug's effects on humans is carried out by way of different successive and interrelated stages. As these must be carefully planned and ethically justified, the clinical trial has been designed as a tool fundamental in the planning and development of these stages.