Before a pharmaceutical company can initiate testing in humans, it must conduct extensive preclinical or laboratory research. This research typically involves years of experiments in animal and human cells. The compounds are also extensively tested in animals. If this stage of testing is successful, an organisation will then request approval to begin testing the drug in people.
The clinical testing of experimental drugs is normally done in three phases, each successive phase involving a larger number of people. In addition, pharmaceutical companies also carry out post-marketing or late phase three/phase four studies.
A Phase One Study:
Phase I studies are primarily concerned with assessing the drug's safety. This initial phase of testing in humans is done in a small number of healthy volunteers (20 to 100), who are usually paid for participating in the study. The study is designed to determine what happens to the drug in the human body--how it is absorbed, metabolized, and excreted. A phase I study will investigate side effects that occur as dosage levels are increased. This initial phase of testing typically takes several months. About 70 percent of experimental drugs pass this initial phase of testing.
A Phase Two Study:
Once a drug has been shown to be safe, it must be tested to see if it works . This second phase of testing may last from several months to two years, and involve up to several hundred patients. Only about 30 to 35 per cent of experimental drugs successfully complete both phase I and phase II studies. Most phase II studies are randomized and blinded trials
A Phase Three Study:
In a phase III study, a drug is tested in several hundred to several thousand patients. This large-scale testing provides the pharmaceutical company with a more thorough understanding of the drug's effectiveness, benefits, and the side affects it may have. Most phase III studies are randomized and blinded trials.
Phase III studies typically last several years. 70 to 90 percent of drugs that enter phase III studies successfully complete this phase of testing. Once a phase III study is successfully completed, a pharmaceutical company can apply for approval to market the drug.
What is a randomised control trial?
Most phase II and all phase III trials are randomised trials. One group of patients will receive the experimental drug, while a second control group will receive a standard treatment or placebo. A placebo is a treatment that looks the same as the experimental drug but has no effect on the body, it is a dummy pill. Often these studies are blinded or "double-blinded"
What is a control group?
A group of clinical trial participants that receives the placebo or standard therapy for a condition while another group is given the experimental treatment. The control group serves as a measuring stick to gauge the effectiveness of the experimental treatment.
What is a blind trial?
A blind trial is one in which the participant is not told which arm experimental or control of the clinical trial he or she is on.
What is a double-blind trial?
A clinical trial in which neither the participants receiving the treatments nor the researchers administering the treatments are aware of which group is receiving the experimental treatment. The purpose is to eliminate any bias in reporting of results.
