Storage stability of serum formulations containing ofloxacin for autologous serum eardrop therapy

The storage stability of serum formulations containing ofloxacin for autologous serum eardrop therapy was evaluated for microbiological quality and component stability.

Sterile serum formulations were prepared by mixing human serum and ofloxacin otic solution (1:1, v/v). To simulate eardrop contamination with external ear surface substances, prepared serum formulations were contaminated with a cotton swab that was rubbed sufficiently on the human external ear. Formulations were stored at 4 °C or room temperature in the dark. Colony forming units (CFUs), ofloxacin, and basic fibroblast growth factor (bFGF) concentrations in the stored serum formulations were determined.

The growth of microorganisms derived from the external ear was not detected in serum formulations after storage for 14 days, regardless of temperature. However, microbial growth was detected in serum formulations stored without ofloxacin, indicating that this is necessary for storage. In addition, concentrations of ofloxacin and bFGF did not decrease over 14 days, indicating that ofloxacin and bFGF in serum formulations are stable for this time period.

The present study indicates that the efficacy and safety of serum formulations used as a therapy for perforated eardrums are stable and safe for at least 14 days.