Sterility Test Conditions for Purified Sodium Hyaluronate Injection Evaluated via Membrane Filtration.

Sterile preparations require a sterility test, commonly performed by membrane filtration (MF) or direct inoculation (DI) as specified in pharmacopeias. MF is the preferred method for filterable aqueous preparations because of its high sensitivity, and DI is often used to test devices due to the difficulty in eluting microorganisms from the surfaces. A recent amendment to International Organization for Standardization 11737-2 now permits MF for liquid products of medical devices. Injections of hyaluronic acid (HA) are listed as drugs in the Japanese Pharmacopoeia (JP), but are classified as liquid products of medical devices in Europe and the U.S.A. The JP mandates DI for HA-based injections. HA-based injections for osteoarthritis were recently considered for reclassification as drugs in the United States because of their anti-inflammatory, analgesic, and chondroprotective effects. This study examined the suitability of MF and DI for sterility testing of an HA-based injection product. In DI, the maximum allowable volume of HA-based injection was set at 0.25 mg/mL of HA in the culture medium. All tested bacterial and fungal growths in media supplemented with 0.25 mg/mL of HA were observed within 3 d (bacteria) and 5 d (fungi). In MF, the injection was diluted with 0.1% peptone-0.1% polysorbate 80 solution. The solution was filtered, and the membrane was washed twice. All tested bacterial and fungal growths were observed in the culture medium. For the sterility test of the HA-based injection product, no growth was observed after 14 d of incubation in both methods. In conclusion, both DI and MF are suitable for sterility testing of HA-based injections.