Radiopharmaceuticals are drugs that contain radioactive isotopes and are used for diagnosis or therapy. Their mechanism of action depends on their intended use:

For diagnosis: Radiopharmaceuticals are designed to target specific organs, tissues, or cellular receptors. Once administered into the body, they emit radiation (usually gamma rays or positrons) that can be detected by imaging devices such as PET or SPECT scanners. This allows doctors to visualize physiological processes and detect abnormalities like tumors or organ dysfunction.

For therapy: Therapeutic radiopharmaceuticals deliver targeted radiation (often alpha or beta particles) directly to diseased cells, such as cancer cells. The radiation damages the DNA of these cells, leading to their destruction while minimizing harm to surrounding healthy tissues.

The effectiveness of radiopharmaceuticals lies in their ability to combine targeting molecules (such as peptides, antibodies, or small molecules) with radioactive isotopes, achieving precise diagnosis and treatment at the molecular level.