those of human medicine and this enables premium products to be developed.
Supplied on an individual basis, companion animal products cover a wide range
of more expensive constituents. Examples include bronchodilating aerosols for
airway disease, spot-on anti-parasiticides, and novel drugs for the management of
obesity and separation anxiety. Apart from economic considerations, owner conve-
nience and improved compliance are factors in developing formulations and
devices for particular routes of delivery.
In human medicine, cost-effective, convenient, low frequency oral administra-
tion dominates the market, whereas in veterinary medicine many owners baulk at
administering tablets to cats and dogs and prefer palatable or chewable formula-
tions which can be placed in food or taken voluntarily from the hand. Likewise,
while human patients are relatively accepting of nasal and pulmonary delivery for
themselves, few veterinarians would advocate nasal or pulmonary delivery to cats
as compliance is likely to be poor. Nonetheless, there are well-established proce-
dures for administration of volatile (or gaseous) anaesthetics by inhalation. In
addition, companion animal research has the potential to benefit from physiological
similarities between monogastric animals and humans, thus enabling transfer from
the more advanced human drug development sector (Riviere 2007 ). For example,
skin patches have been highly successful in human medicine for a range of
passively absorbed drugs, including nicotine, oestrogen and oxybutynin (reviewed
in Ball and Smith 2008 ), and more recently as iontophoretic transdermal systems
for fentanyl (Herndon 2007 ) and lignocaine (Dixit et al. 2007 ). On the other hand,
the use in veterinary medicine of similar systems is at least partially confounded by
fur, feathers or scales, the possibility of accidental oral ingestion, altered integu-
mental physiology and high cost. Nonetheless, skin patches of fentanyl (smaller
versions of the patch approved for human use, Duragesic 1 ) are used in dogs to
alleviate post-operative pain (Egger et al. 2007 ).
Overall, advances in veterinary drug delivery are constrained by relatively small
market sizes for comparatively few classes of drugs and therefore economic con-
siderations limit investment. Ultimately, the transfer or adaptation of human drug
delivery technology is a possible option for the veterinary sector, but in practice it
is uncommon due to differences in physiology and drug pharmacokinetics and a
Table 1Target animal groups with applications ranging across experimental, therapeutic,
husbandry, population management, and public health fields
Animal populations Market requirements
Companion Similar to human (principal differences reflect varied anatomy and (patho)
physiology, together with issues of compliance)
Domestic (Food
producting)
Cheap, effective, safe to administer and low residues in edible tissuesSports Similar to human athletes
Laboratory Initial studies for human applications for pharmacodynamic and
pharmacokinetic (drug delivery) discoveries and product development
Wild Cheap, effective, typically challenging with respect to delivery and
environmental contamination
Drug Delivery Systems in Domestic Animal Species 81