Úvod Patients What is a clinical trial

What is a clinical trial

Any investigation in human subjects intended to discover or verify the clinical, pharmacological and/or other pharmacodynamic effects of an investigational product(s), and/or to identify any adverse reactions to an investigational product(s), and/or to study absorption, distribution, metabolism, and excretion of an investigational product(s) with the object of ascertaining its safety and/or efficacy.

Participation is voluntary and, as this is a research study, results cannot be guaranteed.

Human Clinical Trial Phases:

I Phase

Phase I of a clinical trial assesses the safety of a drug or device. This initial phase of testing, which can take several months to complete, usually includes a small number of healthy volunteers (20 to 100). The study is designed to determine the effects of the drug or device on humans including how it is absorbed, metabolized, and excreted and also the side effects.

II Phase

Phase II of a clinical trial tests the efficacy of a drug or device. This second phase of testing can last from several months to two years, and includes larger numbers of patients (100-300). Most phase II studies are randomized trials where one group of patients receives the experimental drug, while a second group receives a standard treatment or placebo. Often these studies are “blinded” which means that neither the patients nor the investigator know who has received the experimental drug.

III Phase

Phase III of a clinical trial compares a new drug to the standard-of-care drug.This phase usually involves up to 3,000 participants who have the condition that the new medication is meant to treat. Trials in this phase can last for several years. This stage proves the safety of the drug or device and its efficacy in treating people who have the condition for which it was developed. Phase III of a clinical trial may be divided into phases IIIa and IIIb as well.

IV Phase

Phase IV of a clinical trial is performed after a drug product has been approved. These trials are often called post-marketing (post-registration) studies. The purposes of these trials are to identify differences between a new pharmaceutical product and other drugs in this pharmacological group, to compare its efficacy with already marketed analogs, and to demonstrate a new drug benefit in relation to health economics and to identify and determine previously unknown or ill-considered side effects as well. As a result, the safety and efficacy of a drug may be reviewed periodically according to new clinical data on its use.


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James Lind was a Scottish naval surgeon, and he found himself on a Royal Navy ship full of sailors sick with scurvy. His ideas helped us to understand how to test which treatment might work best. His work not only saved lives on his ship, but helped to lay the foundation for modern clinical trials – randomised controlled trials – as we know them today.