Stability of stock and diluted rituximab

Purpose: The stability of two rituximab preparations stored in polyvinyl chloride (PVC) bags at 4 °C for up to 14 days was investigated. Methods: Two types of test samples were prepared: (1) 10 mL of rituximab solution (10 mg/mL) drawn directly from the original manufacturer's vial and injected into sterile glass vials and (2) 3 mL of rituximab 10 mg/mL mixed with 17 mL of 0.9% sodium chloride injection and injected into sterile PVC bags. Samples were analyzed immediately after preparation and after storage at 4 °C for 3, 7, and 14 days. Ritux-imab activity at the designated time points was measured using a validated enzyme-linked immunosorbent assay (ELISA) method. Chemical stability was defined as the retention of ≥85% of the drug's initial activity. Physical stability was evaluated through visual inspection for color changes or precipitate formation under normal laboratory lighting. Results: The results of ELISA testing (with spectrophotometric absorbance assessment) indicated that the percentage of initial rituximab activity retained was over 85% for both test preparations under the storage conditions evaluated; no changes in color or turbidity were observed in any of the test samples. These findings suggest that extending the expiration dating of both stock and diluted rituximab solutions beyond the manufacturer-specified limit of 24 hours is feasible. Conclusion: Rituximab 10 mg/mL undiluted in glass vials and 1.5 mg/mL diluted in 0.9% sodium chloride injection in PVC bags are stable at 4 °C for up to 14 days.