The ready-to-fill, like prefillable glass syringes are washed, siliconized, sterilized and packaged with the primary packaging manufacturer. They are able to then be filled by the pharmaceutical companies with no further processing.
Overview of Siliconization Process:
The method starts with the washing with the inside of the vials. An aqueous emulsion of an polydimethysiloxanic oil (conforming to all or any pharmacopoeias) is then sprayed inside vials. Finally, the silicone film is applied onto the glass by passing the treated vials from the annealing lehr.
Differences between free and baked-in silicone ? What must be recommended ?
• Main difference will be the method of putting on silicone oil:
- Direct spray of medical grade silicone
- Spray of medical grade silicone oil emulsion and thermal treatment to evaporate solvent (water) and decompose emulsion stabilizers.
Both method end-up with presence of silicone oil layer at the glass surface. Baking-in process supports uniform distribution of lower quantity of silicone
• Little difference in materials of construction from different vendors/processes; some differences in thermal treatment conditions for baked-in silicon.
• Selection of solution depends upon target product profile ( staked-in needle vs luer; manual use vs auto-injector/pen, …).
• Promissing alternative approaches (beyond limiting/controlling silicone quantity and uniformity, and fixation by heat) which should still provide adequate functional performance (i.e. gliding and sealing) and lower potential silicone oil interactions at the same time:
- Cross-linked silicones
- Solid lubrication ( coated stoppers on non-lubricated containers).Other watch outs/ takeaway
• Needle clogging difficulties with high concentration biotherapeutics. Role of tip closure still to get assessed: possible watch-outs Extractable/Leacheables profile, WTR rate)
• Free radical content container system and potential impact deriving from sterilization mode.
• Oxygen permeability of closure system.
The inner barrel from the prefilled syringe is often lubricated/siliconized by the syringe supplier or in the syringe filling site. Syringe siliconization can be a complex process demanding automation which has a high level of precision; this information is often deemed "know-how" which is rarely published.
The optimization in the siliconization process necessitates reliable qualitative and quantitative analysis methods. Online methods for the one-hundred percent control of siliconization during production are not currently available. In process control, random samples are taken and many destructive and non-destructive methods are utilized
There is a trend towards reduced-silicone systems or baked-on siliconization in glass syringe finishing. Improved analysis techniques along with a better understanding of the phenomena involved support optimized usage of silicone oil.
