What are phases of Clinical Trials?
These are the stages of drug developments with increasing information on human safety and effectiveness. There are four phases of trials and the results of one phase help to plan the next. Conducting trials in phases helps to minimize risk by exposing limited number of subjects at each stage and generate sufficient data for further studies. Of these phases three are conducted for regulatory approval of the drug or device and the fourth phase is conducted after marketing.
Pre regulatory clinical trials are been divided into 3 Phases:
Phase I: These are also known as Human Pharmacology. This is the most crucial phase since the new drug is given for the first time to a small group of healthy human volunteers under close medical supervision to assess the tolerability and toxicity at selected doses. The pharmacokinetic and pharmacodynamic parameters are studied to establish the safety of the new drug in human being. This study may be done with increasing doses or repeating single doses.
Phase II: These are known as Exploratory Trials. After the drug has been proved safe in phase I, it is tested on few hundred patients to assess the therapeutic effectiveness and safety. Both improvement in disease symptoms and adverse effects are observed and recorded on structured sheets called Case Report Form.
Phase III: These are also known as Confirmatory Trials. The studies are conducted in a larger number of patients and the efficacy and safety of the new drug is compared with a standard drug based on predefined criterion. This phase is conducted at multiple sites and includes few thousand patients who resemble end users. Majority of the time and money spent on clinical development is in this phase.
Following the marketing of new drug, studies to confirm its efficacy and safety continue and are known as Phase IV.
Phase IV: These studies are also known as Post Marketing Surveillance studies, as these are conducted after the new drug has been approved for marketing. The aim of phase four studies is to know the safety profile after the drug has been used in the population at large. It also helps to identify rare adverse effects which cannot not be captured during initial phases. This helps to optimize the use of new drug for increasing therapeutic benefit or reducing risks.
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