A series of tests through which all drugs must pass to determine their effectiveness and safety. There are many phases to clinical trials:
Preclinical trials: Testing for the toxicity and effectiveness of substances in non-human subjects
Phase 0: Use of a small number of human test subjects and tiny dosages to check how easily drugs are absorbed into the body and how long they stay there before being broken down
Phase I: Healthy volunteers are used to double-check the safety of the drug by slowly increasing the dosage
Phase II: A group of 100-300 patients are tested to determine if the drug has a therapeutic effect
Phase III: Further testing using a large patient sample is undertaken
If the drug passes through all these stages, it is then ready to be marketed for public use.