In cats with a free roaming lifestyle it is often necessary
to accept a less stringent level of glycaemic control than in dogs. Fortunately
as cats rarely develop cataracts and show less marked postprandial hyperglycaemia
this is not usually a problem and a degree of control that eliminates clinical
signs and allows maintenance of stable body weight is usually attainable.
Two thirds of diabetic cats require insulin; oral hypoglycaemics and diet
can be considered
for overweight cats or for those whose owners cannot manage injections.
Diet
There has been much interest recently in low carbohydrate high protein diets
for diabetic cats, they are formulated on a similar principle to the Atkins's
diet, hence the name Catkin's diets! These include Royal Canin diabetic
and Hills m/d. These are a more natural diet for cats that are after all
obligate carnivores. One American study found cats fed this type of diet
had better glycaemic control, lower insulin requirements and were more likely
to discontinue insulin all together. Prior to this work there was also some
evidence for the use of high fibre diets in diabetic cats. Therefore both
types of diets can be tried; the high fibre ones should not be used in thin
cats. Many cats can also be successfully stabilised on their usual food.
For cats used to being fed twice daily this can continue with one meal given
with the morning injection and the second one either with the second injection,
or 6-8 hours later for those on SID therapy. If the cat prefers to snack
this can continue.
Insulin
There are two choices of insulin for cats, either PZI (Insuvet) or
lente (Insuvet or Caninsulin).
PZI can be used once or twice daily; lente forms must be used twice daily.
Caninsulin comes in small vials which saves wastage as really a vial should
be discarded a month after opening, also the syringes designed for this
enable more accurate dosing in small pets. Recommended starting doses are
1-2 iu/cat/dose for all types. With twice-daily regimes the injections should
be 10-12 hours apart.
Initial routines for stabilisation - There are two main
choices:
Minimalist regime
· Start the diet and insulin therapy
· Every 2 weeks examine the cat, check appetite, thirst, weight,
serum fructosamine
· Adjust insulin by 0.5-1 unit per dose accordingly
· Once the cat appears clinically stable and has an acceptable fructosamine
(usually 350-450 nmol/l) decrease the check ups to q6-12
weeks.
· For indoor cats the owner can also test the urine for glucose and
ketones eg weekly
In depth regime
· Start diet and insulin therapy
· Every 3 days check blood glucose at the estimated nadir (4-6
hours post injection) Aim for 5-14 mmol/l. Increase by 0.5-1iu
per dose as necessary.
· Test fructosamine every 2 weeks
· Once the cat appears stable and the blood glucose is within the
acceptable range perform a blood glucose curve.
· Long term check ups every 6-12 weeks with a nadir glucose and fructosamine
are usually appropriate, further curves are only required if instability
is suspected
Glucose curves
If a cat suffers from stress hyperglycaemia this will be a pointless exercise!
A glucose curve is performed by testing every 2 hours for one interinsulin
injection period. This helps establish whether the insulin is lasting long
enough, giving good control all day and the ideal time to perform any future
nadirs. Human glucometers are invaluable for measurement of blood glucose,
some owners are now able to use these at home, this minimises stress for
the cat. Ideally they should receive instruction from their vet before using
these and it is important they still liase with their clinic for advice
on dose adjustment.
Treatment of non insulin dependant diabetes mellitus
This is only appropriate for clinically well, non-ketotic cats that are
obese or of normal bodyweight. A combination of oral hypoglycaemics and
diet are used (see above for diets). The aim of the drugs is to stimulate
insulin secretion from the pancreas therefore the pancreas must have some
functional capacity. The most commonly used group of drugs are the sulphonylureas
e.g. glipizide (Glibinese), they are not licensed.
· Give glipizide 2.5mg BID with food. May need to increase to 5mg
BID. May take 1-2 months to take effect.
· Check after 2 weeks; ideally test blood glucose, liver enzymes,
serum fructosamine
· Side effects can include vomiting, hypoglycaemia, raised liver
enzymes, and jaundice
· If the cat becomes unwell at any time or ketotic it must be given
insulin. |