STABILITY OF FOSPHENYTOIN SODIUM WITH INTRAVENOUS SOLUTIONS IN GLASS BOTTLES, POLYVINYL-CHLORIDE BAGS, AND POLYPROPYLENE SYRINGES

OBJECTIVE: To determine the stability of fosphenytoin sodium admixture s with NaCl 0.9% injection and dextrose 5% (D5W) injection when stored in glass or polyvinyl chloride (PVC) containers, to evaluate the comp atibility of fosphenytoin with 11 other intravenous solutions, and to determine the stability of fosphenytoin repackaged in polypropylene sy ringes. METHODS: Dilutions Of fosphenytoin sodium 1, 8, and 20 mg phen ytoin sodium equivalents (PE)/mL were prepared in NaCl 0.9%, D5W, and 11 other intravenous fluids. Aliquots of each solution in NaCL 0.9% or D5W were transferred to three glass bottles for storage at 25 degrees C and 21 PVC bags for storage at 25, 4, or -20 degrees C. Aliquots of each admixture with the other intravenous fluids were transferred to three PVC bags and stored at 25 degrees C for 7 days. In addition, 63 syringes were filled with fosphenytoin sodium 50 mg PE/mL (undiluted) and stored at 25, 4, or -20 degrees C. Samples of each solution from t he three containers were analyzed for visual compatibility, pH, and fo sphenytoin concentration initially and at 0.5, 1, 2, 3, 7, 14, and 30 days during storage at 25 and 4 degrees C and at 1, 7, 14, and 30 days during storage at -20 degrees C. Following removal of containers from the freezer, additional samples were obtained after 7 days at 4 or 25 degrees C, and 7 days at 25 degrees C, and then 7 days at -20 degrees C. RESULTS: No visible precipitation or change in color or clarity wa s observed in any of the fosphenytoin solutions during the study. The concentration of fosphenytoin at each sampling time remained within 97 -104% of initial concentration, regardless of container, concentration , intravenous admixture, or storage temperature. CONCLUSIONS: Fospheny toin sodium, either undiluted in polypropylene syringes or diluted wit h NaCl 0.9% or D5W in PVC bags, remains stable for at least 30 days at room temperature, under refrigeration, or frozen, After removal from the freezer, fosphenytoin can be thawed, kept at 4 or 25 degrees C for 7 days, and then returned to the freezer for another 7 days. Admixtur es of fosphenytoin sodium in various other intravenous fluids are stab le for at least 7 days at room temperature.