Stability of an extemporaneously prepared recombinant human interferon alfa-2b eye drop formulation.

PURPOSE The stability of an extemporaneously prepared recombinant human interferon alfa-2b (rh-IFN-alpha2b) eye drop formulation was studied. METHODS A volume of 3 x 10(6) International Units (IU) of rh-IFN-alpha2b formulated in solution was diluted with 5 mL of a 0.01% benzalkonium chloride solution. The stability of the extemporaneous formulation was evaluated for 30 days at room temperature (5 +/- 3 degrees C) and at 28 +/- 2 degrees C. Solutions were periodically subjected to bioactivity assay (antiviral titration), enzyme-linked immunosorbent assay, preservative-efficacy and sterility testing, organoleptic evaluation, and pH testing. Preservative efficacy was tested against five microorganisms. The organoleptic characteristics were verified by checking for the transparency and absence of suspended solids against light and dark backgrounds. Statistical significance was determined using analysis of variance after a comparison of the homogeneity of variance (Bartlett's test). RESULTS Results from this evaluation indicated that the formulation was stable for 15 days at 5 +/- 3 C. During this storage period, the biological activity varied between 80 and 125% of the nominal value (0.5 x 10(6) IU/mL). The formulation was sterile and organoleptically acceptable. The pH ranged from 6.7 to 7.3, and the preservative was effective. The formulation was stable for 7 days when stored at 28 +/- 2 degrees C. The formulation remained sterile, colorless, and without suspended solids. The pH range was 6.7-7.3. CONCLUSION An extemporaneously pre -pared rh-IFN-alpha2b eye drop formulation was stable at 5 +/- 3 degrees C for 15 days and at 28 +/- 2 degrees C for 7 days.