Evaluation of plasmapheresis on the removal of tobramycin

A 26-year-old man with thrombotic thrombocytopenic purpura resulting in respiratory and renal failure was treated with plasmapheresis (PP). Coexisting pulmonary infiltrates were empirically treated as pneumonia with various antibiotics, including vancomycin and tobramycin. The half-life of tobramycin was 6.93 hours. During PP the half-life of tobramycin decreased to 4.47 hours as determined by three random levels. The fraction eliminated due to PP was 35.5% and the fraction cleared by PP was 10.9%. We conclude that PP contributed significantly to the total clearance of tobramycin. The need for supplemental doses must be evaluated in each patient based on post-PP serum concentrations.