Biomedical Engineering Reference
In-Depth Information
errors are minimized (Schoenknecht and Romacker, 2005). Prefilled syringes
are sterile devices filled with drug formulation under aseptic conditions. A
syringe shown in Figure 1 comprises a barrel, covered needle and a plunger to
push the medical solution through the needle after removing the lid (DeGrazio,
2005). Compared to conventional syringes, prefilled systems require less
overfill and subsequently 18-23% of the dose can be saved (Thorpe, 2005). An
annual growth of approximately 20% in the US market of prefilled syringes
has been reported (Abdelkader et al., 2005). The first commercialized prefilled
syringes were those of heparin and produced by Sanofi and RhÔne Poulence-
Rorer in the 1980s (Schoenknecht and Romacker, 2005).
(Adapted from: DeGrazio, 2005).
Figure 1. A prefilled syringe comprising a plunger, a barrel to store the medical liquid
and a needle covered by a lid.
Unfortunately, the oily silicone used as a lubricant coating in the
manufacturing process of prefilled syringes can interact with some
biotechnology products. For instance, silicone oil has been found to cause
protein denaturation and aggregation (Jones et al., 2005), which might be
attributed to the tendency of proteins to get adsorbed onto the oil/water
interface. This reduces the amount of drug delivered to patient. Surfactants
have been found to reduce the protein aggregation, possibly by competing with
the protein molecules on the interfaces (Thirumangalathu et al., 2009). The
interaction between the plunger and medical solutions is less problematic for
conventional syringes since the residence time of drug solution in the syringe
is very short (e.g. less than 1 min). However, the prefilled syringes are not
only devices but also packaging systems for long-term storage. Thus, possible
incompatibilities between the formulation and the plunger should be seriously
considered. Previously, it has been found that the reactivity of the silicone
coating is determined by the number of terminal hydroxyl groups present
