Oral administration is the most natural route of drug administration and there
are many examples of interspecies differences in the modalities of oral administra-
tion that are linked to some aspects of feeding behaviour. There are also many
examples illustrating that a rational drug formulation can take advantage of some
species–specific factor. This is the case for some oral formulations developed for
dogs and cats. Pets are often difficult to medicate due to owner inability or
reluctance to administer injectable formulations, and for some chronic treatments
(for example, cardiovascular therapy, alternate day corticotherapy) only the oral
route is a realistic option. Administration of oral preparations such as tablets or
capsules to dogs or cats by inserting a tablet directly in the mouth requires owner
skill; in a survey of 95 dog owners, it was reported that only 44% achieved 100%
compliance in administering an oral antibiotic treatment for 10 days (Maddison
1999 ). Thus, with increased use of chronic medications in dogs and cats, there was a
need for highly palatable solid oral dosage forms which would be voluntarily
accepted either from a feeding bowl or from the outstretched hand of the pet
owner (Thombre 2004 ). This became feasible due to specific carnivore behaviours
regarding attitude to new food.
During evolution, food behaviour adaptation allowed animals to select carefully
their food through a variety of sensorial and inherited or learned behavioural
mechanisms (Bradshaw 2006 ). Neophobia and neophilia are two contrasting feeding
strategies. Neophobia is the fear and rejection of new food. In contrast, neophilia
is the interest and preference for any new food providing an opportunity to eat new
food in case of food shortage. Both are important to the survival of wild species.
Neophilia is often found in dogs, especially in such breeds as Labrador retrievers and
Cavalier King Charles spaniels. This opportunistic feeding behaviour enabled appe-
tent formulations to be developed and now in the veterinary market many appetent
formulations exist for non-steroidal anti-inflammatory drugs (NSAIDs), angiotensin
converting enzyme (ACE) inhibitors, etc. for companion animal therapy. There are
however important differences between the dog and the cat regarding taste. The dog
is rather insensitive to salt, whilst the cat is insensitive to sugar (Bradshaw 2006 ).
It is known that cats prefer fish and dogs prefer beef, pork, and lamb to chicken, liver,
and horsemeat. These findings are utilised when formulating palatable oral tablets by
adding food-based products or flavour ingredients.
In contrast, neophobia protects animals against toxic substances. Neophobia is
typically observed in non-vomiting species, such as rodents and horses and this
makes it difficult to administer any drug requiring voluntary ingestion. Therefore,
gavage or naso-gastric intubation may be required. Alternatively, the drug must be
hidden in bait as, for example, in rodenticide substances. In horses, drugs are
traditionally mixed with bran in some appetent mash to facilitate voluntary inges-
tion, because placing the drug as a powder directly on to food is generally not
appropriate in this species, as the horse displays sniffing behaviour towards any
odorous foreign substances.
A unique feature of veterinary medicine is the case of collective treatments.
Veterinary drugs may be administered to food-producing animals (pigs, poultry,
cattle, sheep, etc.) either individually or, more often, at a herd or flock level. For
Species Differences in Pharmacokinetics and Pharmacodynamics 25