Clinical trials are essential for evaluating the quality, efficacy, and safety of new medicinal products and are necessary for the authorization of new active substances. These trials follow preclinical studies conducted on cells and animals to ensure the product's non-toxicity.
Clinical trials are divided into four phases, which sometimes overlap:
Phase 0: assessment of pharmacokinetics, particularly oral bioavailability and half-life of the drug in small, subtherapeutic doses in a very small number of patients. Often skipped for Phase I.
Phase I: involves a small group of healthy volunteers (less than 100), mainly to assess safety and optimal dosing, except in certain cases like cancer where affected patients are involved from the start.
Phase II: testing of drug on participants (100–300 participants with a specific disease) to assess efficacy (therapeutic effect is not assumed before) and side effects.
Phase III: testing of drug on participants (300–3,000 people with a specific disease) to assess efficacy, effectiveness and safety (therapeutic effect is assumed).
Phase IV: post marketing surveillance in public to monitor long-term effects and detect rare side-effects.
Quality criteria for clinical trials include having both a treatment group and a control group, where the latter receives a placebo or an established product without participants' knowledge. This process, known as "blinding," and random assignment to groups are crucial for unbiased results. Voluntary participation and the option to withdraw at any time are also fundamental principles of clinical trials.
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