The full form of IMP in Medical is Investigational Medicinal products. By definition, Investigational Medicinal Product is a medicinal product used or tested under a clinical trial. Investigational Medicinal Products not only have new drugs, but they may also have old drugs being tested for new diseases or conditions. In many cases, IMP may also have the same drug with a new formulation or packaging.
There are very strict guidelines from the regulatory agencies regarding the manufacturing and handling of Investigational Medicinal Products. This is to ensure that public safety is maintained and that clinical data is collected accurately. The IMP should not reach the public until the authorities have approved it. This is the reason why every country is very strict about managing IMP. The medicine can be dangerous until the evaluation is complete.
Other full forms of IMP: