Stability of alcohol-free theophylline liquid repackaged in plastic oral syringes

The stability of an alcohol-free liquid theophylline product repackaged and stored in polypropylene oral syringes was studied. A commercially available alcohol-free liquid theophylline preparation was repackaged in the following unit dose syringes: 3- and 10-mL clear polypropylene syringes and 3- and 10-mL amber polypropylene syringes. Fifty syringes of each type were prepared. The 3-mL syringes were filled with 2 mL of theophylline, while the 10-mL syringes were filled with 7 mL of the liquid. All syringes were stored at room temperature under continuous fluorescent lighting. The mean volume of theophylline delivered from six syringes of each type was determined on days 0, 14, 30, 60, 90, and 180 after repackaging. The samples were assayed for theophylline content by high-performance liquid chromatography. The theophylline dose delivered ranged from 96.2% to 101.7% of the initial repackaged dose. The difference in theophylline concentrations remaining among the types of syringes after 180 days of storage was not significant. The volume of theophylline delivered decreased and the concentration increased as a probable result of water evaporation over time. Alcohol-free theophylline liquid repackaged in 3- and 10-mL clear or amber disposable polypropylene unit dose syringes can be stored at room temperature under continuous fluorescent light for at least 180 days.