Before any clinical trial takes place, there has to be a new method or drug to test. Researchers toil away in the lab to develop new drugs: performing studies on the molecular level, genetically engineering drugs using computers and testing the drug using human or animal cells.
Researchers might examine how a certain substance interacts with an individual hormone or with a particular receptor on a cell wall. If the research is fruitful and a new method is shown to have treatment potential, it is first tested on live animals (with regulatory oversight) such as guinea pigs or rats to see if it's toxic or if unexpected side effects develop. These animals may be bred or designed to have the condition that is being tested, such as low testosterone, high blood pressure or cancer. Animals are also given the new treatment prior to mating to see if the treatment adversely affects reproduction or causes birth defects. This research is shown to a regulatory body (in the U.S., it's the Food and Drug Administration). Once approved, the new drug then undergoes what is supposed to be (but isn't always) a rigorous testing regimen consisting of several phases:
- Phase I tests the new treatment in small quantities on a small number of people (fewer than 100) to determine if it's safe, if it has side effects, and to learn how it's metabolized by the body. Phase I involves very close medical supervision.
- Phase II usually involves several hundred volunteers to determine if the drug (now deemed safe) is effective as a treatment. Researchers will increase dosage to find the minimum and maximum amounts that can be safely delivered while still being effective.
- Phase III trials are conducted to see if the drug is more effective than similar treatments already available. Often, they're tested against placebos, and just as often they fail to outperform them. While most drugs that reach this stage move on to the market, as many as three in 10 don't [source: CenterWatch].
- Phase IV trials occur after the drug has gone to market and can last for many years. Thousands of volunteers are tested, and sometimes drugs are pulled off the market because serious drawbacks are discovered even in this late stage of testing.