The advantage of using positron emission tomography in drug research.

A large problem in drug discovery is to find relevant in vitro or in vivo animal models and to be able to extrapolate the results obtained to humans. Drug research now benefits from the fast development of imaging technologies that trace radiolabelled molecules directly in the human brain. Positron emission tomography (PET) and allied techniques use molecules that are labelled with short-lived radioisotopes and injected intravenously. The most straightforward approach is to radiolabel a new potential drug and then to trace its anatomical distribution and binding in the brain. An indirect approach is to study how the unlabelled drug inhibits specific radioligand binding. The demonstration of quantitative relationships between drug binding in vivo and drug effects in patients is used to validate targets for drug action and to optimize clinical treatment.