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HIV/AIDS Glossary

Phase 4 Trial

Testing in humans that occurs after a drug (or other treatment) has already been approved by the Food and Drug Administration (FDA) and is being marketed for sale. Phase 4 trials are conducted to determine long-term safety and effectiveness and to identify adverse effects that may not have been apparent in prior trials. Thousands of participants are usually recruited to volunteer for this phase of clinical testing.

Related Term(s): Clinical Trial, Food and Drug Administration, Phase 1 Trial, Phase 2 Trial, Phase 3 Trial, Preclinical


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The fifth step of a clinical trial

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