Metabolism of Sr⁵⁸ and Ca⁴⁵ in man after single and multiple doses

¹ Veterans Administration Hospital, Hines, Illinois

Three patients received single doses of Sr⁸⁵ and one Ca⁴⁵ as well, the plasma levels, and urinary and fecal excretions being followed for 3–4 weeks. Calculations were then made to predict plasma levels and excretions following the administration of 12 small doses to each patient, and values predicted were compared with those found. Changes in calcium metabolism limited the predictive value of single-dose data, but when variations in urinary calcium could be allowed for, predicted and found values agreed well. The factors involved in extrapolation from single to multiple doses are discussed. Within certain limitations, the extrapolation appears valid and may be applicable to the problems involved in the investigation of Sr⁹⁰ as well, although the fact that the latter is ingested over long periods of time makes comparison with single-dose data more hazardous.