Stabilization of epinephrine in a local anesthetic injectable solution using reduced levels of sodium metabisulfite and edta

Abstract

The effect of sodium metabisulfite concentration upon the stability of epinephrine in a Lidocaine HCl with Epinephrine solution was evaluated using an elevated temperature (60°C) screen for up to 35 days. Long term room temperature data (23°C) was collected and evaluated for up to forty months and substantiated the results observed in the accelerated studies. Enhancement of the epinephrine chemical stability was predicated upon a tenfold reduction in the metabisulfite level from 0.05% to 0.005% plus the inclusion of a specific chelating agent, disodium edetate, into the formula. Protection from light is of optimum importance since more rapid photolytic degradation occurred in the experimental formula than in the control. In two distinct packages, 20 ml glass vials and 1.8 ml glass cartridges, the epinephrine stability was found to be significantly improved (p < 0.05) compared to a control, suggesting the possibility of increased expiration dating.