Stability of heparin and physical compatibility of heparin/antibiotic solutions in concentrations appropriate for antibiotic lock therapy.

OBJECTIVES The purpose of this study was to determine the biological stability of heparin and to test for physical compatibility in heparin/antibiotic solutions in concentrations suitable for antibiotic lock therapy. METHODS Solutions were prepared with heparin 5000 U/mL or heparin 10 U/mL and cefazolin 10 mg/mL, ampicillin 10 mg/mL, or piperacillin 40 mg/mL. Solutions of vancomycin 2.5 mg/mL with heparin 5000 U/mL and vancomycin 2 mg/mL with heparin 10 U/mL were also prepared. The ability of each solution to elevate the activated partial thromboplastin time (APTT) of pooled normal plasma and the physical compatibility of the solutions were assessed for 14 days. RESULTS The APTT levels never varied by more than 16.4% from baseline. Physical incompatibility never occurred before day 14 in any of the solutions. CONCLUSIONS Mixing of antibiotics in the concentrations chosen for the study had no clinically significant effect on biological heparin activity, and all solutions were physically compatible for at least 14 days.