Flucloxacillin Drug-Level Samplings from Central Line Catheter Versus Peripheral Veins

The aim of this study was to compare flucloxacillin concentrations between two specimens collected simultaneously during continuous infusion. One specimen was collected from a peripherally inserted central catheter (PICC) and the other collected simultaneously by peripheral venepuncture. We conducted a prospective study in seven patients who were enrolled in our outpatient parenteral antibiotic therapy (OPAT) service at John Hunter Hospital, Australia, and who were receiving continuous flucloxacillin infusions from an elastomeric device. Blood samples were drawn simultaneously from a PICC and a peripheral vein in each patient. Plasma drug concentrations were measured and compared by paired t test. Flucloxacillin concentrations from the patient’s PICC sample were disproportionately higher than the peripheral sample with a mean difference of 28.4 mg/L (95%CI 2.48 to 54.4; p = 0.037). Plasma flucloxacillin concentrations taken from central catheters are falsely elevated as compared with those from peripheral veins.