Clinical trials are designed to test whether or not a new drug or medical device works and is safe.
There are four stages of drug development. The first is preclinical. Preclinical is the laboratory development of drug and includes testing in animals. For psychiatry drugs, there are not many good animal models. The animal test is mainly for toxicity and to get a basic idea of how the drug is metabolized; that is, cleared from the body. The clinical trial starts with phase 1 studies. They are small and use normal, healthy volunteers. These studies are designed to determine how the drug is metabolized, the side effects, and the highest dose tolerated. These studies are conducted under very close supervision and constant monitoring of vital signs, EKG’s and blood chemistry. Closely examined are the drug metabolism and maximum plasma levels following a dose, and duration of drug staying in the body. The FDA monitors the results and determines if the drug can proceed phase 2. Phase 2 studies are done in the patient population that it intends to treat. The total number needed is around 300 patients, so the drug company pays multiple sites to do he study and the data is pooled. Statistics are used to interpret the data. Pooling of multiple site data causes a lot of problems, but the statistics corrects for this. The basic question is: does the study drug work better than no drug (placebo). During phase 2, safety, metabolic, and efficacy data (how well it works) are collected. There has to be a placebo group to compare to the drug group. The investigator is blinded to drug assignment. This blindness has to be maintained to ensure integrity of the study. The gold standard study is called “double blinded, placebo-controlled, parallel study”. Parallel means this study is only compared to patients in this particular study and not any other study even if very similar. Phase 3 studies are very similar to phase 2 except the number of patients is greater. Phase 3 is most interested in efficacy. However, safety data is still aggressively obtained. Where phase 2 may have one hundred to two hundred patients, phase 3 may have a thousand. Phase 4 studies are generally after a drug has been FDA approved. This may be to see if a different dose is indicated. They do not require as much safety data since the drug is already approved and toxicity is basically known.