which the animal is suffering. A major factor in the development of meaningful
evaluations is the familiarity that observers have with the behavioural character-
istics of the particular animal. This generally means that much more specific
evaluations can be made on those species that are the closest “companions” of
humans, such as dogs, cats and horses and, to a lesser extent, farm animals and other
pet animals. It is only recently that pain behaviour in non-mammalian species has
received significant consideration, and the information on wild species is still very
limited.
2.4 Analgesic Strategies and Techniques
The strategies to deal with pain in animals have tended to follow those developed
for human medicine. These fall into several groups. The first strategy has been to
adopt procedures intended to lessen the development of pain; this applies particu-
larly to surgical interventions but also to methods such as physiotherapy and other
supportive measures and to techniques which lessen the likelihood of injury. One
technique, which is particular to non-human animals, is that of genetic selection, the
production of less aggressive breeds of dogs and cattle, the selection of chickens for
better bone growth to match their weight gain and the much more recent drive to
eliminate dog breed characteristics that can give rise to painful malformations
(Editorial 2008 ).
The second strategy, which is probably the best known, is the provision of
analgesic drug therapies. Most of the classes of pharmacological agents used in
humans are currently used in animals, and this has led to the recognition that there
are significant species differences in both the pharmacokinetics and the pharmaco-
dynamics of particular drugs. This leads, in turn, to an imperative that dosage
schedules must be developed not only for particular types and severities of pain
but also on a species-by-species basis.
A third strategy is the utilisation of different routes of administration of analgesic
drugs. Veterinary surgeons have traditionally preferred to use the parenteral route
of administration; intramuscular, intravenous and subcutaneous routes are all com-
monly used. This approach is more associated with the guarantee of dose and timing
compared with the convenience, but potentially greater variability, of oral adminis-
tration, which is generally favoured in human medicine. In addition, the oral route
is generally not preferred in animals with a functional ruminant digestive system,
which can result in more complex pharmacokinetics of drugs administered in this
manner. Also, the oral administration of drugs in either food or water can be
associated with unreliable or unduly variable rates and extents of absorption.
Moreover, the administration of drugs in tablet form to many species can represent
significant challenges. Nevertheless, the oral dosing of some analgesic drug classes
over short-, medium- and long-term durations has become commonplace in the
companion animal species, dogs, cats and horses. This has resulted from the
convenience/necessity of dosing by animal owners in these clinical subjects.
164 A. Livingston