Biomedical Engineering Reference
In-Depth Information
patenting inventions if their exploitation would be contrary to public order or morality. Thus, it is
not possible to patent:
•
the human body;
•
the cloning of humans;
•
the use of human embryos for commercial purposes;
•
modifying germ line identity in humans;
•
modifying the genetic complement of an animal if the modifi cations cause suffering without
resultant substantial medical benefi ts to the animal/to humans.
4.10 Delivery of biopharmaceuticals
An important issue that must be addressed during the preclinical phase of the drug development
process relates to the route by which the drug will be delivered/administered. To date, the vast
majority of biopharmaceuticals approved for general medical use are administered by direct injec-
tion (i.e. parenterally) usually by intravenous (i.v.), subcutaneous (s.c., i.e. directly under the skin)
or intramuscular (i.m., i.e. into muscle tissue) routes. Administration via the s.c. or i.m. route is
generally followed by slow release of the drug from its depot site into the bloodstream. Amongst
the few exceptions to this parenteral route are the enzyme DNase, used to treat cystic fi brosis
(Chapter 12), and platelet-derived growth factor (PDGF), used to treat certain skin ulcers (Chapter
10). However, neither of these products is required to reach the bloodstream in order to achieve its
therapeutic effect. In fact, in each case the delivery system delivers the biopharmaceutical directly
to its site of action (DNase is delivered directly to the lungs via aerosol inhalation, and PDGF is
applied topically, i.e. directly on the ulcer surface, as a gel).
Parenteral administration is not perceived as a problem in the context of drugs which are
administered infrequently, or as a once-off dose to a patient. However, in the case of products
administered frequently/daily (e.g. insulin to diabetics), non-parenteral delivery routes would
be preferred. Such routes would be more convenient, less invasive, less painful and generally
would achieve better patient compliance. Alternative potential delivery routes include oral, nasal,
transmucosal, transdermal or pulmonary routes. Although such routes have proven possible in the
context of many drugs, routine administration of biopharmaceuticals by such means has proven
to be technically challenging. Obstacles encountered include their high molecular mass, their
susceptibility to enzymatic inactivation and their potential to aggregate.
4.10.1 Oral delivery systems
Oral delivery is usually the preferred system for drug delivery, owing to its convenience and the
high level of associated patient compliance generally attained. Biopharmaceutical delivery via this
route has proven problematic for a number of reasons:
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