Protein binding of five platinum compounds. Comparison of two ultrafiltration systems

Amicon Centriflo CF50A cones and Amicon MPS-1 micropartition systems with YMT filters were compared for the preparation of ultrafiltrates of plasma samples containing cisplatin, spiroplatin, JM-40, carboplatin or iproplatin. The MPS-1 system equipped with YMT membranes showed less adsorption of the platinum compounds than CF50A cones and allowed more rapid processing of smaller plasma volumes. In vitro binding to human plasma proteins measured with YMT filters after 24 h of incubation was 94%, 89%, 83%, 31% and 0 for cisplatin, spiroplatin, JM-40, carboplatin and iproplatin, respectively. These values corresponded with the initial half-lives in plasma and the decomposition half-lives of intact drug in plasma ultrafiltrate as measured by HPLC. It is suggested that the degree of protein binding is related to the stability of the leaving groups.