Biomedical Engineering Reference
In-Depth Information
technologies became increasingly sophisticated controlled drug-delivery
products diversii ed further into: subcutaneous implants, buccal sys-
tems, vaginal rings, and wafers. Technological sophistication enabled
new approaches to drug delivery systems beyond transdermal patches to
address highly specii c needs; in particular, therapies that stood to ben-
ei t from more invasive drug-delivery solutions than transdermal drug
delivery.
Transdermal patches account for over 60% of all controlled drug deliv-
ery systems available in the market. h e technology of transdermal patches
has been extensively described elsewhere [93-95]. Because they of er an
alternative for controlled delivery of substances into the bloodstream
through the skin, this is particularly suited for the delivery of potent drugs
that would be poorly absorbed or extensively metabolized when adminis-
tered orally.
h eir initial adoption can be explained by their ease-of-use, conve-
nience, and increased patient compliance. h e i rst generation of trans-
dermal patches was essentially limited by the passive methods of drug
dif usion to deliver small, lipophilic, low-dose drugs [95]. However, the
next generation introduced the use of chemical enhancers, noncavita-
tional ultrasound, and iontophoresis to facilitate drug delivery [93, 95].
Iontophoretic systems facilitate the dif usion of larger molecules with a
residual electric current that helps widen skin pores. h e third generation
is currently under clinical trials and is expected to revolutionize the deliv-
ery of large molecules and vaccines [93-98].
2.7
Infections Associated with Medical Devices
Infection is dei ned as a homeostatic imbalance between the host tissue
and the presence of microorganisms at a concentration that exceeds 105
organisms per gram of tissue [99]. h e emergence of infection is associated
with a large variety of wound occurrences, ranging from traumatic skin
tears and burns to chronic ulcers and complications following surgery and
device implantations. If the wound setting is able to overcome the microor-
ganism invasion by a sui cient immune response, then the wound should
heal via the common four-phased process of coagulation, inl ammation,
proliferation and remodeling [100]. If not, the formation of an infection
can seriously limit the wound healing process, interfering with wound clo-
sure and even leading to bacteremia, sepsis and multisystem failure.
h e insertion or implantation of medical devices has become an indis-
pensable part in almost all i elds of medicine. However, medical devices are
