An Exploratory Study of a New Vancomycin Eye Drops Formulation for Extemporaneous Compounding

Compounded eye drop solutions of vancomycin hydrochloride have important clinical applications, such as postoperative antimicrobial prophylaxis and bacterial keratitis. There exists a plethora of data to support the use of various liquid vehicles to compound vancomycin hydrochloride eye drops. However, there are a number of limitations for implementation, especially the frequent shortage or discontinuation of the vehicle products. This study was designed to investigate the use of an OTC eye wash product as the evergreen vehicle and to evaluate the physical and chemical stability of the new formulation.

The Advance Eye Relief^® eye wash and vancomycin hydrochloride for injection vials were used to prepare 10 and 50 mg/mL vancomycin eye drop solutions. The solutions were packaged in Steri-Droppers^® bottles and stored in a freezer for 14 days followed by 28 days in refrigeration. The 14-day period of freezing was included to allow time for sterility testing. At pre-determined stability time points, samples were taken for visual inspection, pH and osmolality measurement, and analysis by a stability-indicating high performance liquid chromatography (HPLC) method.

Freshly prepared vancomycin eye drops were clear, colorless, and free of particulates. The pH readings were 7.03 and 6.28 for the 10 and 50 mg/mL solutions, respectively. The osmolality of both solutions were within the range of 300-330 mOsmol/kg and considered isotonic. Initial drug concentrations of all samples were confirmed by HPLC to be within 100%-103% of the label claims. Throughout the stability study period, there were no significant changes in the appearance, pH, or osmolality of any samples. The HPLC results also confirmed that the drug concentrations in all stability samples were within 98%-101% of the initial time zero values and no significant degradation product peaks were observed.

A new compounded vancomycin eye drop formulation was developed to mitigate vehicle sourcing issues. This eye drop formulation was easy to prepare, exhibited satisfactory properties for ophthalmic applications, and remained stable chemically and physically when stored for 14 days in freezer followed by 28 days in refrigerator.