Tritium 3H, a radioactive isotope of hydrogen, is commonly used in medicinal chemistry as a label to follow the course of a drug in the human body. Chemists like to use the technique to evaluate drug candidates and their metabolism. A team led of researchers at the Max-Planck-Institut für Kohlenforschung in Mühlheim, Germany, has now found a new way to label complex small molecules with tritium. In a joint research project with the research and early development organization of the Swiss pharmaceutical company Roche, they investigated ways to incorporate tritium into pharmaceuticals and other similar molecules that are important derivatives for drug development.