Radioactive pharmaceuticals

Abstract

It is important to use radioactive isotopes with no beta raciiations, or with low energy beta radiations. Because scintillation detectors which effectively measure only gamma radiation are most often used, beta radiation contributes to radiation dosage but provides no data. Special pharmaceutical problems associated with radiopharmaceuticals are:(1) problems of carrier-free state, ie., those arising because of the extremely small chemical quantities; (2) problems of self-decomposition, produced by the effect of radiation on the compound itself or on its solvent; (3) problems resulting from isotope effect, i.e., differences in reaction rates that sometimes result from differences in atomic weight of isotopes; and (4) problems resulting from chemical differences betwecn labeled and naturally occurring compounds.

Smith’s “Internal Dose Calculation for 99mTc”: An Excellent Paper with Approximate Methods (perspective on “Internal Dose Calculation for 99mTc” J Nucl Med. 1965;6:231–251)

“…An illustrative example would be an uremic patient who is to have a renal scan with 203 Hg Neohydrin. The hepatic uptake of the radiopharmaceutical in this case is greatly increased (40), resulting in an unexpectedly high absorbed dose to the liver, as compared to the absorbed dose calculated based on the kinetics of Neohydrin for normal individuals.…”