In Phase I trials the new / experimental drug or treatment is tried out on a small group (20-80) of healthy human subjects for the first time , after it has been well tested in lab and animal studies. This initial phase of testing typically takes several months.
The main purpose of this phase is to evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics of the new treatment or the new drug on humans and the side effects associated with increasing doses and also to determine what dosages patients can take without causing them harm.
When compared to the later phases of the clinical trial, phase I studies, carry significant risks, however it is a very important phase as the information gained in this phase of the study, about a potential treatment's effects in patients and any early findings on its effectiveness are critical for the design of later-phase studies.
Phase -I drug trials are mostly conducted in inpatient clinics where the participant is continuously monitored by medical staff.
Phase -I trials can be further divided into two types:
Single Ascending Dose studies ( SAD )
Multiple Ascending Dose studies ( MAD )