Qualitative models are introduced to analyze safety and effectiveness in the economic way. Case reports are weakest form of clinical evidence. These are usually published after a clinician notice a problem and associate that problem with exposure drug. A case report can be strengthened by a relating ADR to drug concentration in the body. Case series is a group or cluster of case reports that may be generated by a single clinician, group of clinician, a hospital, pharmaceutical company or a regulatory agency. These reports allow a closer examination of the problem, but provide little insight into the rates of occurrence or extent of the problem. Survey of drug use, Due to limitation of availability of data, these types of studies are introduced which gives general utilization data for a large area.