What are Phase IV clinical trials commonly referred to in the US?

Phase IV clinical trials are often referred to as postmarketing research trials because they occur after a drug has received approval from regulatory authorities and is available on the market. These trials are critical for monitoring the long-term efficacy and safety of the medication in a larger and more diverse population than was possible during earlier phases of clinical testing.

In Phase IV, researchers gather additional data on how the drug performs in real-world conditions, identify any rare or long-term side effects, and assess the drug's effectiveness across different demographics and use cases. This phase helps to ensure that the benefits continue to outweigh any risks associated with the drug after it is widely prescribed.

While preclinical trials involve laboratory and animal studies before human trials begin, and randomized controlled trials are often used in earlier phases to establish efficacy and safety, postmarketing research specifically addresses the drug's performance in the general population once it is commercially available. Experimental drug studies pertain more to the investigational stages where therapies are being tested for the first time. Thus, the designation of Phase IV trials as postmarketing research trials highlights their role in ongoing safety surveillance and efficacy assessment post-approval.