Low-temperature sterilization of Novelia^® eye drops vials: feasibility, content-container interactions and functional impact

Introduction
Novelia^® eye drops vials (NADV) are supplied in sterile batches of 28 units. Once opened, the batch sterility is not maintained unless used immediately under aseptic conditions. The aim of this study was to investigate the feasibility of low-temperature sterilization (LTS) of NADVs, its effectiveness, the presence of residues of the sterilizing agent (hydrogen peroxide or H₂O₂), the impact of LTS on the content-container interaction and its impact on the functionality of NADVs.

Materials and methods
New NADV (NEMERA) were packed in double layer of Ultra^® pouches (AMCOR) and subjected to 2 types of LTS cycles (Stericool, Getinge): rapid cycle (H₂O₂ 59%, 31 min; n=3) and standard cycle (H₂O₂ 82%, 48 min; n=3). Following sterilization, the residual H₂O₂ level was measured in the double pouches of the NADVs using a Draëger X-AM 5100 probe. The inside of the NADVs was then washed with 1mL H₂O. The H₂O₂ present in this extract was assessed by a semi-quantitative measurement using MQuant^® strips (0-25ppm, Supelco). The interaction of NADV with the sterilizing agent (H₂O₂) and the possibility of organic matter release was assessed by quantifying Total Organic Carbon (TOC): 10mL of 0.9% NaCl was introduced into sterilized (rapid cycle) and non-sterilized (n=3/modality) NADVs, stored for 28 days at room temperature, then the TOC of the contents was analyzed in accordance with standard NF EN 1484 (Shimadzu TOC analyzer, linearity 0.5-10 mg/L). Maintenance of the sterile state was assessed by a sterility test (European Pharmacopoeia 2.6.1) at 3 and 6 months post-sterilization. To study the impact of LTS on the ability of NADVs to remain sterile once opened, sterilized VNTs were prepared under aseptic conditions and loaded with BSS (Balanced Salt Solution, Alcon) and stored at 2-8°C, 25°C or warm conditions (32°C-35°C): 2 drops of each solution are extracted each day and incubated in Trypticase Soya and Thioglycolate broths, at day 7, 14, 21 and 28.

Results
Hydrogen peroxide residues persisted in the NADV with the standard cycle (0.5 to 2ppm extractable and 0.1 to 2.3 ppm measurable), while it was not the case with the rapid cycle ([H₂O₂]< detection limit): the rapid cycle was retained for the rest of the study. Assessment of TOC with and without sterilization showed no release of organic matter after sterilization. The sterility test showed that the sterile state of NADV packaged in double sachets was maintained for at least 6 months. Finally, the sterilized and BSS-loaded NADVs stored under different temperature conditions retained their functionality, with the contents remaining sterile for at least 28 days.

Conclusion
NADVs can be sterilized by LTS without any risk of residual hydrogen peroxide and without releasing organic matter from the container, maintaining a sterile state for at least 6 months and without affecting their functional characteristics.