The participation in clinical trials as a test person is always voluntarily! According to the definition, a clinical trial is the use of a new substance in humans to obtain information about its therapeutic or diagnostic value for a given disease. In addition, information about safety of use and tolerability will be collected. The development of new drugs is separated into four phases:

• phase I trials:

  After substantial testing in animals, the drug is administered to healthy volunteers who are called "subjects". "Subjects" are people who have agreed to participate in clinical trials with substances (that are not approved yet) for the purpose of collecting information about the tolerability, effect, safety, pharmacokinetics (appearance and disappearance of the substance in the blood), and pharmacodynamics (appearance and disappearance of the effect) of the investigated substance.

• phase II trials:

  In phase II trials the drug candidate is used in patients for the first time. These patients have the disease where the application of the new drug should provide benefits as compared to the standard treatments. It is the indent of these studies to prove the efficacy and dose-response relationship as well as the safety of the new drug.

• phase III trails:

  The drug is tested in a larger patient population. The goal is to collect data on safety and efficacy in long-term clinical use as well as information about possible side effects.
  
  After phase III the new drug is submitted for registration based on the information obtained in all trials so far.

• phase IV trails:

  These trials are performed after the registration of the drug to collect further information about the clinical benefits and possible adverse side effects, and to broaden the medical indications of the substance.