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Veterinarians currently employ two main strategies for
managing pain in companion animals. The
first strategy is pre-emptive analgesia.
This involves giving pain medication before the patient is exposed
to the painful procedure. The
second strategy is multi-modality therapy.
As the name implies, this strategy takes advantage of the fact that
various classes of analgesic drugs have additive or synergistic effects
when administered together. The
rationale is to combine drugs that disrupt the development of pain at the
various individual steps along the pain pathway.
There are several
pharmacologic classes of drugs available to treat pain.
Opioids, alpha-2 agonists, non-steroidal anti-inflammatory drugs,
local anesthetics, and adjuvant analgesic agents have all been
employed in controlling animal pain. One particular class of drugs, the
non-steroidal anti-inflammatory drugs (NSAIDS), is very effective in
controlling post-surgical pain as well as pain and inflammation due to
arthritis. Unfortunately,
cats are particularly susceptible to exhibiting adverse effects from this
class of drugs, which includes aspirin and acetaminophen, both of which
can be harmful, and even lethal, to cats.
How
NSAIDs work
The NSAIDs control pain by
inhibiting an enzyme called cyclo-oxygenase (COX). Several years ago, it was discovered that there were two
forms of this enzyme, COX-1 and COX-2.
We now know that the COX-1 enzyme is continuously produced by the
body and is mostly responsible for generating compounds that are
beneficial, such as maintaining blood flow to the kidneys and protecting
the stomach lining. COX-2, on
the other hand, is mainly responsible for generating compounds that
contribute to pain and inflammation.
The traditional NSAIDs, such as aspirin, inhibit both COX-1 (the
“good” enzyme) and COX-2 (the “bad” enzyme).
The newer NSAIDs are designed to inhibit the bad one, COX-2, while
having minimal effect on COX-1. In
the past few years, several COX-2 specific drugs have been marketed for
people and for dogs, but very few have been
suitable for cats.
New drug
The U.S Food and
Drug Administration initially approved meloxicam (brand name: Metacam;
manufactured by Merial, Ltd.), for control of pain and inflammation
associated with canine arthritis. The drug had been used in many other
countries, however, in an off-label manner to treat pain in cats as
well. It no longer needs to be used off-label. Injectable meloxicam is
now approved for use in cats in the U.S.
Advantages
Meloxicam is not the only
NSAID that can be given to cats. Others,
such as aspirin, carprofen, ketoprofen, and piroxicam have been given to
cats, with varying degrees of success, and more importantly, with varying
complications. Some of these
NSAIDs cause gastric upset (aspirin, piroxicam), some exist primarily as
injectable formulations and cannot be given orally. Except for aspirin, these NSAIDs are not intended for
long-term use. A major advantage of meloxicam is that it comes as an oral
formulation and can be given long term to manage post-surgical pain,
inflammation and discomfort due to arthritis, and pain associated with
cancer.
Poor
Little Louie
Louie is a 5 year-old Maine Coon owned by Louise Roussin.
Louie has a painful oral condition called lymphoplasmacytic
gingivitis. This is an
auto-immune disorder in which the gums become extremely inflamed, tender,
and painful. When medical
management with antibiotics and steroids can no longer control the
condition, extraction of all the teeth behind the canines is recommended.
Louie was losing his battle with this disease.
Oral pain was affecting his ability to eat and his demeanor.
I gave him a ketoprofen injection several hours before the
procedure (pre-emptive analgesia) and an injection of a narcotic pain
reliever at the end of the procedure and again four hours later
(multi-modality therapy). That evening, Louie’s face was a little swollen, and of
course he had no interest in food. The
following morning, Louie was feeling great.
He was affectionate, rubbing his face against the cage and
demanding attention from me and my staff.
I gave him another injection of ketoprofen and sent him home that
evening.
Ms. Roussin called two days later.
Louie was eating softened food, although he was acting sluggish and
aloof, and this was very unusual. Concerned
that oral discomfort from the multiple extractions might be affecting his
demeanor, I prescribed meloxicam once daily for the following three days.
Ms. Roussin called on day 3 to tell me that Louie immediately
returned to his sweet, affectionate self as soon as the medication was
administered. This was my
first experience using meloxicam, and I now dispense one dose of meloxicam
after every dental procedure, and additional doses if any extractions were
performed.
Conclusion
It
is now recognized that animals perceive pain much the same way that humans
do, and that we have a moral obligation to protect pets from pain and
suffering. This increased
understanding has driven the need to develop more effective methods of
controlling feline pain, and veterinarians should now be able to control
pain in virtually all feline patients.
Updated 2/9/06
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