4 Phases of Clinical Trials

Phase 1

Phase I trials assess a medication’s safety. These trials also evaluate what the drug does to our bodies as well as what our bodies do to the drug. These effects are called pharmacodynamics and pharmacokinetics, respectively. This first phase of testing in human beings is performed in a very small number of healthy volunteers who and are ordinarily remunerated for their participation. A phase 1 trial will also investigate side effects and benefits that occur at various dosages. Phase 1 trials typically take several months to complete.

Phase 2

After phase 1, when a medication has been shown to be safe, it is then further tested for efficacy. Phase 2 trials can take months to years to complete, and can involve several hundred subjects. These trials are typically “randomized”, meaning that people are spit into two groups, those who receive the drug, and those who receive a placebo.

Sometimes these trials are “double blinded”; neither the patient nor the researcher knows who is receiving the real medication. This enables the trial to be unbiased, producing more accurate results.

Phase 3

In a phase 3 trial, a drug is tested in many more people, typically hundreds to even thousands. With such a large group being studied, both pharmaceutical companies and the FDA gain a better understanding of the medication’s effectiveness, as well as its potential to trigger adverse reactions. These trials are usually both randomized and double blinded, and can last several years. After a phase 3 trial has been successfully completed, pharmaceutical companies can request FDA approval to market the drug.

When such a trial successfully gains FDA approval, it is often known as a “pivotal” phase 3 clinical trial.

Phase 4

Phase 4 trials are performed with FDA approved medications in order to learn even more about an approved medication.


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