MEPERIDINE UPTAKE AND BINDING TO HUMAN BLOOD EX-VIVO

Many drugs are bound to plasma proteins (PR) and/or to erythrocytes (R BC). The RBC count may change due to physiologic factors such as expos ure to high altitude, or pathologic conditions such as anemia or as co nsequence of cancer treatment The purpose of the investigation was to study the influence of 1) drug concentration, and 2) number of RBC on erythrocyte uptake or binding using meperidine as a model drug (M). Hu man RBC concentrated blood was used and blood chemistry determined. Us ing human plasma (P) dilutions were made containing 9.9, 7.62, 5.87 an d 4.11 million RBC mm(3). The whole blood ( WE) samples were spiked wi th M to result in 10, 25, 50 or 75 mu g/ml. Increasing concentrations of M within each group of same RBC count did not influence percentage of erythrocyte uptake/binding. Increase bt RBC count from 4.11 to 9.9 million/mm(3) resulted in significant increase in erythrocyte uptake f rom 77.1% to 94.7% and increase in PR binding from 37.2% to 87.4%.