Biomedical Engineering Reference
In-Depth Information
oral administration. Parenteral delivery may also be needed when oral delivery
is inconvenient (e.g. in patients who have nausea, vomiting or who are
unconscious) or for drugs which have poor oral bioavailability because of
inactivation by the first pass hepatic effect or poor absorption from the
gastrointestinal tract (GIT). When the therapeutic effect needs to be
continuous, for instance, administration of analgesics (pain killers) in patients
who are in pain (e.g. morphine in cancer patients) parenteral infusions may be
needed.
Although parenteral delivery offers many advantages, it has some serious
limitations. Since the onset of effect is immediate, the risk is high if patient is
overdosed. In addition, the drug should be given to the patient by a healthcare
specialist (e.g. nurse), which can increase therapy costs and compromise
patient compliance. Many patients especially children have belonephobia (i.e.
fear of needles). In addition, parenteral drug administration is dangerous if
hygienic conditions are not robustly maintained. Microbial contamination of
medical devices is a serious problem that has to be considered, especially in
parenteral delivery since such harmful bacteria can be directly injected into the
blood stream. Bacterial cells may attach themselves to the surface of medical
devices as biofilms by secreting glue-like compounds which enhance the
adhesiveness of bacteria to the device surfaces, followed by development of
bacterial colonies (O'Gara and Humphreys, 2001). This seems to be
particularly problematic if the device encloses an aqueous solution or
dispersion of the drug. Filling such type of devices should take place under
aseptic conditions (O'Gara and Humphreys, 2001). Another approach for
implanted devices is to impregnate the biomaterials with antimicrobial agents
to prevent microbial colonisation on the implanted device (O'Gara and
Humpheys, 2001).
2.1. Prefilled Syringes
For parenteral injections, glass ampoules are traditionally used as
packaging systems of sterile water for injections. The neck of the ampoule is
broken to pull the liquid by a needle and syringe and reconstitute a freeze-
dried powder of the drug. This procedure may result in the contamination of
the preparation with tiny glass particles. Thus, using safe alternatives to the
conventional ampoules is highly desirable.
Prefilled syringes have been introduced as safe alternatives to glass vials
and ampoules since contamination with glass particles is avoided and dosing
