Radiopharmaceuticals are drugs that contain radioactive isotopes and are used as diagnostic and therapeutic agents.  Radioisotopes with short half-lives are most commonly used to minimize radiation exposure to patients. In most cases, these short-lived radioisotopes decay to stable elements within minutes, hours, or days, allowing patients to be released from the hospital in a relatively short time.

In some cases, radiopharmaceuticals are used in higher dosage forms to treat some cancers and other diseases. In those cases, the radioactive agent is taken up in the cancerous area and destroys the affected tissue.