Intravenous strontium gluconate as a kinetic marker for calcium in healthy volunteers.

1. We have studied the pharmacokinetics of stable strontium in 10 healthy male volunteers. We gave each volunteer 5 mmol strontium gluconate by intravenous infusion over 1 h and measured strontium concentrations in plasma and urine samples for 20 days. The plasma strontium concentration vs time data for each volunteer were fitted by a triexponential function using NONLIN. Compartmental model-dependent and model-independent pharmacokinetic variables were then calculated. 2. The mean half-life we report (5.4 days) is longer than that previously reported (about 2 days), since we continued sampling for 20 days. However, the rates of clearance (CL 9.4 ml min-1. CLR 5.4 ml min-1, and CLNR 4.0 ml min-1) are similar to those previously reported, and the apparent volume of distribution at steady state (64 l) is similar to the values previously reported for the size of the exchangeable pool of both strontium and calcium. 3. The similarities in the pharmacokinetic behavior of strontium and calcium suggest that the in vivo disposition of strontium may be used as a marker of calcium disposition and for studying the effects of drugs such as the calcium antagonists.