After completion of the preclinical phase, drugs undergo several clinical test phases with different requirements before approval is possible.
Phase I - Test series with healthy participants
First in Human: The aim is to establish an overview of physiological reactions (pharmacokinetics) and their effects (pharmacodynamics) - small groups[1] with healthy participants, n = 20-100), conducted in specialized centers. Duration: months to one year.
Phase II - Application on patients
Therapeutic trial phase: Testing the propagated efficacy and gathering initial experience in indication areas, i.e. testing toxicity and therapeutic safety, finding optimal dosages and replication - open, blinded or standard RCT with control group, larger groups n=500-1000, conducted via medical institutions. Duration: six months to two years.
Phase III - Clinical verification
Therapeutic confirmations: Description of curative and palliative effects with systematic evaluation and recording of harmful medium-term adverse drug reactions (ADRs) - multicenter large studies n = 1000-5000, conducted via medical institutions. Duration: Two to five years.
Phase IV - Verification in everyday practice
Life cycle management: Evaluation of real-world data experience with the Pharmakon to define pharmacovigilance. The influence of the respective indications and their beneficial effects should be worked out as reliably as possible. Furthermore, interactions with other drugs and long-term effects must be recorded and documented and a harm assessment of ADRs must be drawn up - health services research with cohort studies. In addition, comparative cost-benefit analyses and health technology assessment reports (HTA) are carried out. Usually takes five to 10 years to record the key aspects.
[1] In the literature, the information on group sizes is inconsistent, which is why the figures given here may well differ from individual studies.
Further information on the scientific approach, research and methodology can also be found on our science pages.
Authors: glt | Rev.: sfm, bga | Editor: pz | last modified June 8, 2025