Phases of clinical trials

Phase 0

Phase 0 clinical trials are preliminary studies designed to obtain information in a short period of time regarding the pharmacology and distribution of a potential drug and its ability to overcome physiological barriers in the body. They are usually conducted using low doses of isotope-labeled therapeutic substances on a population of 10 to 15 healthy volunteers. This makes it possible to obtain more data on the test substance at a lower cost.

Phase I

During a Phase I clinical trial, the first contact between the potential medicinal product and the human body occurs (if the Phase 0 study is omitted). During Phase I, sponsors aim to obtain as much information as possible on the safety of the investigational product, its pharmacokinetics and, in the case of an innovative product, aim to determine the dose that will be used during Phase II and Phase III. Phase I studies are conducted on a population of 20 to 50 healthy volunteers. This allows basic information to be obtained that would allow the Phase II study to proceed.

Phase II

Do rozpoczęcia fazy II może dochodzić dopiero po sukcesywnym zakończeniu fazy I. Badania, które są prowadzone mają na celu ostateczne określenie dawkowania produktu badanego na podstawie obszernego zbadania jego farmakokinetyki oraz potwierdzenie skuteczności produktu leczniczego. Są to badania, które wymagają więcej czasu na realizację i mogą trwać nawet do kilku lat. Populacja, na której są prowadzone badania zazwyczaj szacuje się od 50 do 500 pacjentów cierpiących na badane schorzenie. Po uzyskaniu wszystkich niezbędnych informacji przeprowadza się analizę, w której stosunek korzyści do ryzyka od stosowania badanego produktu decyduje o możliwości rozpoczęcia kolejnego badania w fazie III.

Phase III

The initiation of Phase II can occur only after Phase I has been successfully completed. Studies that are conducted are designed to definitively determine the dosage of the investigational product based on an extensive study of its pharmacokinetics and to confirm the efficacy of the drug product. These are studies that require more time to complete and can take up to several years to complete. The population on which studies are conducted is usually estimated to be between 50 and 500 patients suffering from the condition under study. Once all the necessary information has been obtained, an analysis is conducted in which the benefit-risk ratio from the use of the investigational product determines whether another Phase III trial can be initiated.

Phase IV

Phase IV clinical trials are otherwise known as post-marketing studies because they are conducted after a drug has been approved for marketing. Such studies are designed to confirm the effectiveness and safety of a drug through its long-term intake. These studies are conducted on a large population, so there is an opportunity to detect potential side effects that occur as a result of long-term intake, as well as identify interactions with commonly taken medications.

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