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How are new drugs tested: from bench to bedside.
Before it can be placed on the market, every new drug must prove its effectiveness and its safety. Regulatory bodies such as the European Medicines Agency (EMEA) or the Food and Drug Administration (FDA) of the United States are charged with establishing the procedures for drug trials and seeing to it that they are followed.
Once a drug has been found to be promising, it enters the phase of preclinical research, where it is tested in vitro (that is, in a laboratory, on cell cultures, for example) then in vivo on laboratory animals. This phase is indispensable for ensuring the safety of the first test phases on humans.
If the drug is successful in the preclinical phase, it enters the clinical trial phase. These human drug trials are generally divided into 4 phases.
Phase 1 is the first administration of the drug in humans. In general, its purpose is not to test the effectiveness of the drug, but rather to evaluate its effects on human metabolism, its pharmacokinetics (that is the speed with which the drug is absorbed, distributed, metabolized and excreted by the human body), its dosage and its possible side effects. Phase 1 is generally carried out on 20-80
healthy volunteers. Very small doses of the drug are administered in the beginning, and then progressively increased.
The drugs that successfully pass the first phase of clinical trials go on to phase 2 trials. During these trials, the drug is tested on a small group of patients who suffer from the disease or condition that the drug is supposed to treat. Though this phase is a first assessment of effectiveness, Phase 2 above all allows for the determination of the best doses and modes of administration (oral, intravenous, … ), and for the confirmation of the results of the Phase 1 trials.
Phase 3 is the first phase of the clinical trials where the drug is administered to a larger group of patients. Its purpose is to confirm on a large scale the efficacy and safety of the drug. It may be spread out over several years and involve many thousands of patients. At the end of this phase, the pharmaceutical company submits the request for authorization to market to the authority concerned (FDA, EMEA, …). Basing its decision on the results of phases 1, 2 and 3, the authority may accept, refuse, or ask for further investigation.
Once the drug is on the market, the pharmaceutical company may launch, on its own initiative or upon the request of the authority concerned, a Phase 4 trial. This makes it possible to test the drug in an even larger population or in a specific sub-group, to evaluate the long-term effects of the drug, or even to test it for other indications.
References:
- Lipsky MS, Sharp LK. From idea to market: the drug approval process. J Am Board Fam Pract 2001; 14(5):362-367.
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