AJP - Endocrinology and Metabolism, Vol 261, Issue 3 E415-E417, Copyright © 1991 by American Physiological Society
Radiation exposure from long-lived beta emitters in clinical investigation
B. R. Landau and W. W. Shreeve
Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106.
Potential hazards restrict the use of 14C in clinical investigation.
Nevertheless, 14C, in readily metabolized compounds, continues to be
administered and in relatively large doses. The compounds are converted to
intermediates and products with longer half-lives than their half-lives.
These longer biological half-lives have not always been taken into account,
although calculations of radiation exposure can be markedly altered by
their inclusion. The minimum dose of 14C needed to accomplish a study must
also be considered, and benefits relative to risks in the administration
must be assessed in terms of the kind and total number of subjects
required. Similar considerations apply to the administration of 3H-labeled
compounds. Furthermore, in assessing risks, the limited information
available on the localization and concentration of the isotopes in the body
should be taken into account. There are also concerns with regard to
administrations in growth situations and to an individual on multiple
occasions. Within those constraints, 14C and 3H can be given with relative
safety.
