EFFECTS OF STORAGE ON THE BINDING OF CARBOPLATIN TO PLASMA-PROTEINS

Plasma ultrafiltrates are routinely used in pharmacokinetic studies of carboplatin. Experiments were performed to detect and quantitate arti factual decreases in the platinum concentration of ultrafiltrates prep ared from plasma samples stored at -20 degrees C and -70 degrees C. Ca rboplatin was added to anticoagulated, whole human blood to produce a 20 mu g/ml concentration. Plasma produced from the blood was stored fr ozen at either -20 degrees C or -70 degrees C. Aliquots from each stor age condition were thawed and ultrafiltered once a week for up to 100 days. Platinum concentrations in ultrafiltrates and plasma were determ ined by flameless atomic absorption spectrometry. There was no loss of ultrafilterable platinum in plasma samples stored at -70 degrees C, w hereas there was a steady decrease in free platinum concentration in u ltrafiltrates prepared from plasma samples stored at -20 degrees C. Th ese results imply that pharmacokinetic studies of carboplatin should u se ultrafiltrates prepared immediately or that plasma for such studies should be stored at -70 degrees C, Storage of carboplatin-containing plasma at -20 degrees C and subsequent ultrafiltration is not acceptab le, because measurement of platinum in such ultrafiltrates will be art ifactually low.