A radioactive drug which, when used for therapeutic purposes, typically elicits no physiological response from the patient.

• Characteristics of the Ideal Therapeutic Radiopharmaceutical

            1. Moderately long t_eff (measured in days). For ¹³¹I NaI, t_eff in thyroid = 6 d

            2. Prefer b- particle emitters (high LET) to maximize tissue dose/mCi injected.

            3. Prefer high energy (>1 MeV)

    4. Must have high target:non-target ratio to minimize radiation dose to non-target organs

            5. Prefer rapid excretion of unbound material.

            6. Readily available, inexpensive

            7. Minimal radiation exposure to personnel in contact with patient, i.e., ³²P

• Types of Emissions Used for Therapy

1. alpha particles

2. beta- particles

3. electrons

4. gamma rays

5. X-rays

• Radioisotopes Used for Therapy

        I-131 for treatment of thyroid diseases and lymphoma

        P-32 for treatment of polycythemia vera

        P-32, Sr-89, Sm-153, Re-186 for palliation of pain from bony metastases

        Dy-165, Ho-166 for radiation synovectomy

         Y-90 for treatment of non-Hodgkins's lymphoma and liver metastases from a variety of primary malignancies