Biomedical Engineering Reference
In-Depth Information
which is inversely proportional to the length of the silicone's polymer chain.
Heating the syringe at a specific temperature may cause the chains of silicone
polymers to extend and robustly adhere to the inner walls of the syringe. This
reduces the concentration of silicone needed to coat the syringe and hence the
number of possible silicone available for reacting with the drug is reduced.
This approach of treatment is called ―backed-on silicone‖ (Schoenknecht and
Romacker, 2005). Syringes made of plastic do not seem to be the solution
since phthalates may leach into the product, resulting in possible allergic
reactions to patient (Sharma, 2007). Moreover, phenolic derivatives may leach
from rubber stoppers of syringes (Sharma, 2007). It seems therefore that each
prefilled syringe product should be studied individually for long-term storage
stability.
2.2. Pen Injectors
Pen injectors are single dose parenteral devices for self-administration of
drug solutions and can be manufactured to be either disposable or reusable
(Maia and Araújo, 2002). For instance, insulin pen injectors, introduced in the
1980s, consist of a cartridge, a short needle and a dosing knob that releases a
dose upon actuation of the device. This method offers safe delivery of insulin
with less pain and high dose accuracy and provides an efficient alternative to
the conventional needle and syringe systems (Coscelli et al., 1995; Lteif and
Schwenk, 1999; Maia and Araújo, 2002; Spollett, 2008). Moreover, diabetic
patients can self-administer the required dose without the need to go to the
hospital or clinic, which reduces therapy costs and enhances quality of
patient's life. An example of pen injectors is the Apidra SoloStar
®
pen (Sanofi
Aventis, USA) which is a pocket-fitted pen comprising a prefilled insulin
reservoir, a dose window and dosing knob to set the required dose, followed
by placing the Apidra Pen to the right location on the body and pressing the
injection button to deliver the dose (Figure 2).
2.3. Autoinjectors
Autoinjectors are single-dose spring-loaded syringes for self-
administration of life-saving injections. The patient needs to position the
device in the correct place and press a button for the needle to be automatically
injected and to deliver the loaded dose. Autoinjectors have been developed to
