Topical Insulin in Artificial Tears Stability Study: Short-term Physical, Chemical and Microbiological Stability Study of 0.5 Units (25 IU/mL) of Topical Insulin in Artificial Tears

Topical insulin (TI) at 25 IU/mL effectively normalizes healing of corneal epithelium and dry eye in diabetic patients. We aim to determine physicochemical stability and sterility of TI in sodium hyaluronate 0.18% (TI-artificial tears [AT]) in an eye drop formulation. The physicochemical stability of TI-AT at 5°C±3°C and 30°C±2°C in sterile low-density polyethylene bottles was studied. Samples were put in conditions of simulated use and analyzed weekly for stability parameters (visual inspection, turbidity, ultraviolet spectral absorption, osmolality, and pH) and culture growth. Insulin was quantified using the stability-indicating high-performance liquid chromatographic method with diode-array detection with RP-C18 column, o-nitrophenol as an internal standard, and ultraviolet detection at 214 nm. Stability was set according to British Pharmacopoeia with 90% to 110% of initial concentration (with 95% confidence interval) considered acceptable. All tested physicochemical and sterility parameters remained stable for 1 month in both temperature conditions with stable TI concentrations. Topical insulin-artificial tears is stable in both room temperature and refrigeration. Topical insulin-artificial tears can be prescribed with a 1-month shelf life.