Antibiotic-heparin lock: In vitro antibiotic stability combined with heparin in a central venous catheter

Long-term hemodialysis frequently requires Vascular access through central venous catheters (CVCs). Infection related to these catheters is a signific ant complication The use of an antibiotic-heparin lock could decrease the r isks associated with infected permanent catheters. As an initial step in de veloping an antibiotic-heparin lock, we investigated the in vitro stability of antibiotic-heparin combinations in CVCs. Initially, cefazolin, vancomyc in, ceftazidime, ciprofloxacin 10 mg/ml each, and gentamicin 5 mg/ml were i ncubated separately in glass test tubes in the dark at 37 degrees C for 72 hours. Samples were analyzed spectrophotometrically for stability at 24-hou r intervals. The procedure was repeated with the addition of heparin (final concentration 5000 U/ml in glass test tubes), and the combination was also examined in CVCs. High-performance liquid chromatography analysis was cond ucted on the antibiotic-heparin combinations at 72 hours to confirm the spe ctrophotometric results. Ciprofloxacin produced an immediate precipitate wi th the addition of heparin and was not analyzed further Absorbance values d ecreased for all antibiotics, with the greatest decreases at 72 hours for c efazolin (27.4%), vancomycin (29.7%), ceftazidime (40.2%), and gentamicin ( 8%) when combined with heparin. These decreases were postulated to be secon dary to adsorption of the antibiotics to the luminal surface of the cathete rs because submitting the catheters to ultrasound with 1% sodium bicarbonat e and analyzing the resulting solution for absorbance revealed that some of the drug was recovered. Although free antibiotic in CVC solution was reduc ed, the concentration should be sufficient (approximately 5 mg/ml) to decre ase the frequency of infections associated with CVCs. We conclude that the concentrations of vancomycin, ceftazidime, cefazolin, or gentamicin used in our study should be sufficient for an antibiotic-heparin lock.