if a drug is safe and effective, at what doses it works best and what the side effects are. The organization Pharmaceutical Research and Manufacturers of America estimates that only five in 5,000 compounds that enter preclinical testing make it to human testing, and only one of those five may be safe and effective enough to eventually reach pharmacy shelves. The process has been likened to looking for a needle in a haystack!
Clinical trials are carried out in phases. Phase I determines how much of a new drug or treatment can be safely given to humans. A small number of patients (20-80) are given increasing dosages of the drug or treatment and carefully monitored for side effects. Phase II trials are conducted in even larger groups of people (100-300) to determine whether the new treatment actually destroys or slows progression of the disease and further evaluates the safety of the treatment. Phase III studies are conducted in even larger groups of patients to confirm the drug's effectiveness, monitor side effects, compare it to commonly used treatments and collect information that will allow the drug to be used safely. Following Phase III trials, FDA approval for marketing or rejection of the drug may occur. Following approval, Phase IV post-marketing studies are often initiated, which enable additional information about the drug's risks, benefits and optimal use to be gathered.