ABSTRACT
The possible path that a radiopharmaceutical follows inside the human body and its final bio-distribution, post-administration, is governed by the pharmacokinetics as well as the physical-chemical properties of the selected radionuclide. The challenge of the kinetic events is the rapid metabolism of a substance and the maintenance of specific levels of the substance in the various components of its systems. Some physical-chemical properties of the radiolabeled drug are also very important, such as the ionization/oxidation state, the solubility at physiologic pH, and the protein/tissue/cell binding affinity. The simplest route of drug administration from a modeling perspective is a rapid intravenous injection. Protein binding of radiopharmaceuticals is greatly influenced by a number of factors, such as the charge on the radiopharmaceutical molecule, the pH, the nature of the protein, and the concentration of anions in the plasma. PK/PD models can describe the relation between drug dosing, concentration, and efficacy.
