SAFETY OF STABLE-ISOTOPE USE

The increased employment of stable isotope tracers for diagnostic and research purposes frequently raises questions on potential risks assoc iated with their use, which is of particular importance in the paediat ric age group. Biological effects and the potential of adverse events has been evaluated in a large number of animal and, in part, also huma n studies. Possible differences in physical, chemical and biochemical behaviour resulting in kinetic and thermodynamic isotope effects betwe en stable isotopes of the same element are related to the relative dif ferences in atomic weight. Deuterium (H-2), which differs markedly in mass form the predominant hydrogen isotope H-1, may induce serious sid e-effects at high concentrations in body fluids. The threshold dose fo r the occurrence of side-effects lies well above the usual tracer dosa ges for clinical use. In contrast to deuterium. heavier stable isotope s such as C-13, N-15 Or O-18 that differ relatively little in mass fro m the predominant isotopes such as C-12, does not show any adverse bio logical effects even at highest enrichments. Conclusion The doses of s table isotope tracer substances that are used for clinical diagnostic and research purposes appear safe and without any adverse effects. Sta ble isotope tracers should only be used in children if I the tracee is safe at the doses applied, and tracer is chemically pure and stable. In the case of intravenous application, the tracer preparation must al so be sterile and pyrogen free.