Clinical trials are a set of procedures in medical research  conducted to allow safety (or more specifically, information about adverse drug reactions  and adverse effects of other treatments and safety and efficacy 

data to be collected for health interventions (e.g., drugs,

diagnostics, devices, therapy protocols). These trials can take place

only after satisfactory information has been gathered on the quality of

the non-clinical safety, and Health authority/ethics committee approval is granted in the country where the trial is taking place.

Depending on the type of product and the stage of its development,

investigators enroll healthy volunteers and/or patients into small pilot studies initially, followed by larger scale studies in patients that often

compare the new product with the currently prescribed treatment. As

positive safety and efficacy data are gathered, the number of patients

is typically increased. Clinical trials can vary in size from a single

center in one country to multicenter trials in multiple countries.

Due to the sizable cost a full series of clinical trials may incur,

the burden of paying for all the necessary people and services is

usually borne by the sponsor who may be a governmental organization, a pharmaceutical , or biotechnology  company. Since the diversity of roles may exceed resources of the sponsor, often a clinical trial is managed by an outsourced partner such as a contract research organization,site management organization  or a clinical trials unit in the academic sector.