|
| Phase I |
20-100 healthy normal patients |
Up to one year |
Safety |
| Phase II |
Up to several hundred patients |
One to two years |
Safety,
Efficacy |
| Phase III |
Several hundred to several thousand patients |
Two to four years |
Efficacy,
Cost Benefits |
| Phase IV |
Several hundred to several thousand patients |
Two to ten years |
Cost Benefits,
Outcomes |
Source FDA
New medicines are continually being developed for the treatment of disease. It is, however, a complex process with many stages of research and development before a new medicine can be approved by the regulatory authorities and released for the treatment of patients. A promising new drug must be extensively investigated before it is thought to be safe to be given to humans.
Clinical trials play a vital role in the development of new medicines and it is thanks to people volunteering for clinical trials that it is possible for them to be fully investigated and advances in medicine to be made.
In Phase I trials a drug is tested for the first time in a small group of healthy volunteers mainly to determine the early safety profile as well as to gather information on the pattern of drug distribution and absorption, metabolism and other pharmacologic actions of the drug in the body. These studies are carried out at dedicated research facilities, usually hospital based, such as Prime Trials Inc., Vancouver, Canada (www.primetrials.com).
In Phase II clinical trials the drug is tested for the first time in patients with the actual disease condition of interest. In these types of trials information is collected on the initial efficacy of the drug, its optimal dosage and further details concerning its safety. Phase II clinical trials are carried out at multiple investigator sites and are often international.
Phase III clinical trials are large scale, multi-center studies that are carried out in a large number of patients with the target disease. In these types of studies it is important to gather enough data to statistically demonstrate the efficacy of the drug and further safety information. This information is required by the regulatory authorities, who will examine in it in deciding whether to approve the new medicine in their country.
Even after a drug has been approved, clinical studies continue to be conducted in order to gather more information on the drug used in the general population. These types of studies are known as Phase IIIb or Phase IV clinical trials. They are structured to obtain long-term safety data on the drug in specific or additional patient populations, data for different formulations or even to gather economic information on the use of the new drug.
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