fentanyl used in humans have also been used in dogs. However, there may be a need
for re-formulation to ensure optimal use in individual species. This will become
possible as our knowledge of species differences in drug absorption expands
(Riviere and Papich 2001 ). Innovative approaches that have been developed
experimentally include the use of multicompartment microchips containing either
multiple doses of a drug or multiple drugs, which may be released by several
mechanisms (Langer 2001 ). Radio control of such devices introduces further
possibilities.
Advances in technology approaching commercial application are microneedles.
These are structures of such small diameter that puncturing the skin does not
introduce the chance of contamination, nor does it produce any sensation and this
drug delivery mode is therefore classified as non-invasive. Such systems would
permit construction of drug patches for controlled delivery of substances not
normally able to penetrate intact skin (Verbaan et al. 2007 ). Potential applications
range from delivery of therapeutic proteins to genes; the latter could be used to
transform skin cells to secrete systemically available polypeptide hormones, such
as growth hormone and clotting factors (Khavari et al. 2002 ). The development and
commercial application of such systems would fundamentally change the treatment
of chronic deficiency diseases in veterinary patients. Moreover, novel applications
might be particularly appropriate for food producing animals, as chemical residues
associated with traditional dosage forms would not exist. An example of an
application, already taken to proof-of-concept stage, is coating solid microneedles
with antigens for non-invasive vaccine delivery (Widera et al. 2006 ). A problem to
be overcome with all these approaches, when applied to many animal species
compared to humans or pigs that serve as human models, is increased fur density
and variability in skin thickness. These variables make standardisation difficult.
Novel approaches to improved targeting and controlled rate of drug delivery are
already available and have been adopted in human medicine. The additional hurdles
to using such approaches in veterinary medicine are related to economics, involving
the cost of development and sometimes also the cost of manufacture. In addition,
the technology which comes to dominate in human medicine (e.g. electrical
delivery versus microneedles) will determine which of these approaches become
practicable to use in veterinary medicine, a less than desirable manifestation of the
one-medicine concept.
9 Increased Knowledge of Pharmacogenomics
As discussed above and reviewed in chapter, “Pharmacogenomics in Domestic
Animal Species” of this text, advances in the genomic sciences have led to signifi-
cant advances in comparative medicine (Cunningham 2000 ; Semizarov and
Blomme 2009 ). As the genetic code of more species, breeds and microorganisms
is revealed, specific targeting of drugs to species and disease specific endpoints will
become possible. As more data are collected in several species with defined
New Technologies for Application to Veterinary Therapeutics 205