Chemical stability of dexamethasone sodium phosphate after reconstitution in 0.9% sodium chloride injection and storage in polypropylene syringes.

The chemical stability of dexamethasone sodium phosphate (1mg/mL and 0.1 mg/mL) in 0.9% sodium chloride injection was studied at 25 deg C in polypropylene syringes by means of a stability-indicating high-performance liquid chromatographic assay method. The concentrations of the drug were directly related to peak heights, and the percent relative standard deviation based on 5 injections was 1.5. The benzyl alcohol did not interfere with the assay procedure at 278 nm. The products of decomposition separated from the intact drug. At a concentration of 1mg/mL, the loss in potency was 1% after 22 days of storage and less than 3% at a concentration of 0.1mg/mL after storage for 22 days. The pH value of the injection (1mg/mL) decreased from 7.3 to 7.2 after 22 days of storage and from 6.5 to 6.3 in the 0.1-mg/mL sample. The physical appearance of the injection did not change.