VETERINARY practitioners
around the country may have
noticed an empty space on the
pharmacy shelf where they used to
keep Synacthen.
Does that mean they will no longer
be able to diagnose patients with
Cushing’s disease or to monitor their
response to therapy?
Certainly not, according to Ian
Ramsey, one of the UK’s leading
veterinary endocrinologists. The
withdrawal of the product most
commonly used in adrenocorticotropic
hormone stimulation testing should be regarded as an opportunity for
practitioners to brush up on their
clinical skills and recruit help from
their clients to improve the way that
they manage this common endocrine
disorder, he said.
The professor of small animal
medicine at the Glasgow veterinary
school told his audience at VetsNorth
2014 that he is currently receiving
e-mails every day from practitioners
who are concerned about the effects
of the shortage of Synacthen. This
follows the decision last year by the
manufacturer, Novartis, to sell the
marketing rights for the product to the
US company Questcor Pharmaceuticals
which is reserving most of its stocks for use in human patients.
Limited quantities of an equivalent product are available from Dechra
and around half of the audience said
that they had been able to maintain
their supplies. But if and when normal
service is resumed, practitioners are
likely to find that the product will be
considerably more expensive than it
was in the past.
It would make sense, therefore, for
practices to reserve their supplies for
use in managing hypoadrenocorticism
– Addison’s disease – rather than in
cases with excessive production of the
same hormones, he said.
‘Significant shortcomings’
While ACTH stimulation testing is
both a sensitive and speci c tool
for managing dogs with Addison’s
disease, this approach has significant
shortcomings in dealing with Cushing’s
cases.
However, the low cost of the
product in Europe, at about £5 per
vial, has been a factor in maintaining its
popularity among veterinarians faced
with a possible Cushing’s case.
In contrast, their colleagues in the
US and Australia have traditionally had
to pay around $70 for the equivalent
product and so have developed other ways to identify and monitor the
condition.
Those colleagues who are keen
to maintain ACTH stimulation as a
front-line diagnostic test in Cushing’s
cases would be advised to adapt their
methods so that they use much lower
doses of the product, he suggested.
Studies have demonstrated that instead
of using a fixed dose of 250μg, the
same results can be achieved with as
little as 5μg/kg and the rest of the vial
can be divided into suitable volumes
and frozen for future use.
But instead, they were encouraged
to use the alternative low dose
dexamethasone suppression test, which
he believed was more sensitive and had nearly the same specificity as the
ACTH test. The clinician would need
to make sure that the animal does not
experience any stress in the run-up to the test and that the whole of the
dexamethasone dose goes into the
vein, otherwise the results could be
misleading.
Definitive diagnosis?
Prof. Ramsey queried whether it was
even necessary to attempt to get a
definitive diagnosis of Cushing’s
disease in canine patients. In most
cases clinicians could rely on the
overall clinical examination to decide
whether this was a likely diagnosis.
Then they should decide whether or
not treatment was actually necessary.
They should bear in mind that the
condition was unlikely to be fatal –
but if over-treatment precipitates an
Addisonian crisis then that certainly
could be.
The decision would depend on the
attitudes of the owners and the effects
of the dog’s lifestyle on the disease
presentation. Polydipsia and polyuria
were by far the most common clinical
signs. So, “if a dog lives mostly outside,
has free access to water and can urinate
wherever it likes, then the owner will
hardly notice that the animal has the
disease,” he said.
Veterinarians should have more
faith in their clients to provide the information needed to inform
decisions on when to treat canine
Cushing’s cases.
“We have been very lax as a
profession, in making sure that owners
keep a record of their animal’s water
intake and appetite,” he suggested.
Clinicians should ask their clients
about both of these parameters
when the animal is brought into the
consulting room but it is very difficult
for pet owners to remember what
happened weeks or months before, and
so written records are essential.
These measures do not have to be
precise down to the last drop of water
but it should be possible with rough
estimates of fluid intake to identify
overall trends. Studies have shown that
water consumption correlates pretty
closely with the animal’s blood cortisol
levels, he said. Getting the client to
play a more active role in monitoring
their animal’s health also has some
non-medical bene ts. “This engenders
a greater sense of responsibility and
it enhances the human-animal bond
and so it will make your client a better
owner,” he said.
