Atropine and ephedrine adsorption

The purpose of this study was to compare daily changes in the concentration of atropine or ephedrine sulfate solutions that had been stored up to 4 days in plastic or glass syringes. Sets of three plastic and one glass syringe were used for each drug; the glass syringes acted as controls. Each set of syringes was labeled as day 0, 1, 2, 3, or 4. Syringes with medication were laid horizontally, had needles attached, and were stored in the dark at an ambient temperature. Each day, the assigned set of syringes was analyzed by high-performance liquid chromatography. Results showed that the change in the ephedrine sulfate concentration in the plastic syringes from day 0 to day 4 was less than 1.4%. Atropine sulfate decreased 52% over 4 days, with the largest single drop occurring during the first 24 hours. It can be concluded that the two brands of ephedrine sulfate stored up to 4 days at ambient temperature in the brand of syringe used do not significantly decrease in concentration. However, this was not the case with the brand of atropine sulfate studied. The practice of storing atropine sulfate in plastic syringes should be discouraged, because of the possibility of loss of potency due to medication adsorption to syringe plastic.