Stability of somatropin stored in plastic syringes for 28 days

The stability of somatropin stored in two types of plastic syringes was studied. Reconstituted somatropin at high (3.33-mg/mL) and low (1.0-mg/mL) concentrations was stored in polypropylene and propylene-ethylene copolymer syringes at 2-8 degrees C for 28 days. The contents of all syringes were analyzed immediately and at 7, 14, 21, and 28 days by high-performance liquid chromatography for purity, potency, and preservative (m-cresol) content; pH, physical appearance, clarity, and preservative effectiveness were analyzed at the same times. Glass vials of somatropin reconstituted with diluent served as controls. Somatropin did not show significant losses in purity or potency during the 28-day study. m-Cresol concentrations decreased in both types of plastic syrings, more so in the polypropylene syringes, but remained in excess of the minimum required to pass the USP test of preservative effectiveness. On average, the contents of the propylene-ethylene copolymer syringes had greater turbidity than the contents of the polypropylene syringes and, after 21 days, had an unacceptable level of turbidity. No visible particulates were present except at 28 days in high-concentration samples stored in propylene-ethylene copolymer syringes. Somatropin 3.33 and 1.0 mg/mL was stable in polypropylene syringes for up to 28 days and in propylene-ethylene copolymer syringes for up to 14 days when stored at 2-8 degrees C.