Comparative polymyxin B pharmacokinetics in critically ill patients with renal insufficiency and in continuous veno-venous hemodialysis

Purpose The aim of this study was to assess polymyxin B pharmacokinetics (PK) in patients with varying degrees of renal dysfunction and in patients who require continuous veno-venous hemodialysis (CVVHD). Methods The study enrolled 37 patients with sepsis, including 13 patients with glomerular filtration rate (GFR) below 80 mL/min and 11 patients on CVVHD. Each patient received a loading dose of polymyxin B (200-300 mg) and at least 3 subsequent doses of 100-150 mg every 12 h. For every patient, 6-8 blood samples were collected between doses. Polymyxin B (PMB) serum concentration was determined using enzyme-linked immunosorbent assay. Results In sepsis, patients with preserved renal function mean area under the curve over 24 h (AUCO-24 h) value reached 67.8 + 9.8 mg*h/L, while in patients with GFR below 80 mL/min, mean AUCO-24 h was 87 +/- 5.8 mg*h/L. PMB PK in patients with renal insufficiency was characterized by significantly lower clearance (CL) compared to the normal renal function group (2.1 +/- 0.1 L/h vs 3.9 +/- 0.4 L/h respectively). In patients on CVVHD, mean AUCO-24 h was 110.4 +/- 10.3 mg*h/L, while CL reached 2 + 0.23 L/h. The median recovery rate from dialysate constituted 22%. Simulation of different dosage regimens that indicate a fixed maintenance dose of 100 mg ql2h with a loading dose of 200 mg is optimal for patients on CVVHD, and no dosage increase is required. Conclusion This study demonstrates decreased clearance of PMB in patients with renal insufficiency, which puts them at risk of toxicity. Therefore, patients with extremes of renal function might benefit from therapeutic drug monitoring. For patients with anuria, who require CVVHD, we suggest a fixed dose of 100 mg q12h.