To examine the safety and efficacy of new pharmaceuticals, a multi-stage process involving drug discovery, animal studies, and human clinical trials is used. Rare disease medication development entails a lower number of patients, a higher proportion of children, and a more convoluted clinical presentation. Post-approval studies are intended to address a lot of faults that have been identified in rare disease clinical trials. Observational studies, pragmatic trials, and randomized controlled studies are all examples of post-approval research for rare disorders. Original data collecting studies and the utilization of secondary data are both examples of observational studies (retrospective studies). Original data collection can help retrospective investigations overcome restrictions caused by inadequate information in secondary data sources. Disease registries focus on specific health care outcomes associated with a single product and may include a comparator of an alternative therapy or therapies, whereas product-related registries focus on specific health care outcomes associated with a single product and may include a comparator of an alternative therapy or therapies.