Ampuls

The ampul differs from the two previous containers by the absence of a part to be inserted, hence the elimination of this secondary source of potential contamination. The most classical ampul is the open type. For a content volume of 2 mL, the top opening of the ampul has a diameter of 8 mm according to ISO standards (5). This surface is considered as the entry path for contaminant even if a narrow surface of approximately 6 mm is present below.

The classical ampul is processed by washing and a depyrogenation tunnel as for vials. After this process, the ampul must be cooled. Thinner glass means the cooling is more rapid than for glass vials. A good estimate is that the cooling time is approximately 10–15 min, with 6 min without contamination risk because the glass is still hot enough to kill bacteria.

Blow-fill-seal

The concept of BFS is to mold the container, fill it immediately, and seal it, all at the same location (6). This technology minimizes exposure as the container is immediately processed within the same cavity and within a short period of time.

Vials are formed in a mold with vacuum assist applied to the external surface of the container and, in the case of polypropylene resin, a brief blowing pressure applied with sterile air, along with venting. Therefore, for a container of 2 mL capacity, a good estimate is that a net 2 mL of sterile air has been briefly retained inside the container, before the filling step.

The equipment output is approximately one container per cavity every 12 s. During part of this time, approximately 10 s, the mandrel/nozzle is exposed to the controlled environment. The exposed surface is estimated to have a diameter of approximately 8 mm.

Closed vial technology

The filling process for closed vials consists of loading closed and sterile vials, piercing the stopper with a noncoring needle, delivering the liquid, and resealing the stopper with a laser (2).

The two exposed areas are the top of the vial and the needle. The inside of the vial is never directly exposed to the environment. Contamination of the top of the vial could potentially lead to entry of a contaminant during piercing, the contaminant being carried by the needle inside the vial. Therefore, a surface estimated to be equal to the diameter of the needle is considered at risk.

Because indirect contamination by needle carry-over is not obvious, stoppers have been contaminated with 10 bacteria before piercing. That experiment has shown that carry over of contamination can occur, but does so in less than 20% of the cases. In comparison, the statistically calculated result in case of complete carry over would be 48%. Nevertheless, this risk reduction factor has not been taken into account in the calculation.

The exposure time is limited because there is no cleaning or sterilization of the vial before filling. Vials are supplied in boxes of 252 pieces, which are automatically loaded. A good estimate is that 60 vials are in the conveying system from loading table to filling station and that a new box is opened when half a box remains as buffer. According to this calculation, a vial would average 2 min of exposure before being filled. After filling, the stopper returns to position with the two lips of the piercing trace in tight contact. The contact is so tight that most vials can pass a dye test with –300 mbar challenge pressure and entry of a contaminant is considered to be highly improbable. Moreover, laser resealing after filling takes place within few seconds.

A second possible source of contamination could be entry of bacteria during filling through the grooves located on the needle wall. These grooves have been designed to allow exit of the air during filling of the liquid to prevent overpressure inside the vial. As there is a significant airflow moving out of the vial through the grooves, the risk of contaminant entry by these grooves is considered negligible.

The third source of potential contamination is the needle itself. The needle used to fill small volumes has a diameter of 2.0 mm. As the needle penetrates the vial, this penetrating surface is critical. The penetration depth is variable but 15 mm is standard and is used for the model. The cycle time is 2.4 s but the needle is protected inside the vial during approximately 0.8 s.