Antibiotic lock: in vitro stability of gentamicin and sodium citrate stored in dialysis catheters at 37 degrees C

Catheter-related bacteremia (CRB) is a major cause of morbidity and mortality especially among patients receiving hemodialysis. Antibiotic lock therapy represents a promising technique in the treatment of CRB. Several studies have evaluated antibiotics in combination with heparin as an interdialytic locking solution for prophylaxis of CRB. The objective of this study was to evaluate the stability of gentamicin and sodium citrate in hemodialysis catheters as an interdialytic lock. Solutions containing gentamicin 2.5 mg/mL and sodium citrate 40 mg/mL (4%) were prepared individually and in combination. The solutions were instilled into dialysis catheters and stored at 37 degrees C for 96 h. Samples were withdrawn randomly from catheter lumens at 24-hour intervals for 4 days and stored at -20 degrees C until analysis. The samples were analyzed with validated, stability-indicating HPLC assays. The luminal concentration of gentamicin 2.5 mg/mL, sodium citrate 40 mg/mL (4%), and the combination was determined on study days 0, 1, 2, 3, and 4. When gentamicin was combined with sodium citrate and stored at 37 degrees C in dialysis catheters, the solution showed no decrease in either the gentamicin or the sodium citrate concentrations over the 96-hour study period. The percent of the original concentration at 96 h was 102.4+/-1.03 for gentamicin and 102.9+/-1.25 for citrate (P=0.5556). The combination of gentamicin 2.5 mg/mL and sodium citrate 40 mg/mL (4%) can be retained in hemodialysis catheters for at least 96 h at 37 degrees C with no evidence of degradation.