Thank you Julie for sharing this with us. I hadn't seen it either, that I can remember, and I read it all (suggest everyone do the same), and then a couple more times just so I was sure I understood everything.
Just one correction to what Julie said. Although it was published in 2009, the actual study was conducted from 2002-2004. Why that matters is because the PZI mentioned in the study is the discontinued "PZI Vet" that was available up until 2008 or 2009. Not exactly the same as "today's" PZI, which is a compounded form of the old PZI. The "Lente" insulin mentioned in the subject line, in this case was Caninsulin (also called Vetsulin), which is an intermediate length duration insulin more suited to dogs than cats.
http://petdiabetes.wikia.com/wiki/Caninsulin
Caninsulin contains porcine insulin. Porcine insulin is identical to canine insulin[30], but differs from human insulin in respect of one key amino acid. Porcine insulin differs from feline insulin in 3 amino acid positions shown in the table below[31]. Human insulins (i.e. Lantus) differ from from feline insulin by all four key amino acids.
After reading this study, and understanding how it was conducted, (although this might surprise some folks who have seen me in opposition to Lantus in the past), I would probably pick Lantus if the day ever comes when I have another kitty with diabetes.
First off, the study consisted of 24 cats, 8 on each of the 3 insulin types. Originally there were 29, but one of the conditions was that the cat eat the diet specified in the study, and 5 cats wouldn't eat it. I was surprised by the diet actually, which was Purina DM, which is only 7% carbs, but I've read lots of cats just won't eat it after a couple of days.
There are a couple of things that I find troubling however.
What disturbed me....
The initial starting doses for all 3 insulins. Initial dose was determined based on initial BG readings. Kitties with BG above 360 were prescribed one dose, while those under 360 were given half the amount. I guess what troubled me was that the dose was pretty high (not a "start low, go slow" approach which is the suggested starting dose on FDMB). It was based on the cats' weight. For BG over 360, it was .5u/kg of ideal body weight. Under 360 it was .25u/kg ideal body weight. I have no idea really what the average "ideal body weight" of a cat is. Bob weighed 13 pounds (down from 18) at dx. But I'm just going to say he was fat, and guess that ideal would be in the 9-11 pound range to be fair to normal cats.
At a weight between 9-11 pounds, with a BG of 360 or higher, the initial starting dose would be 2u - 2.5u BID, which is a lot higher than what is usually suggested for any insulin - we usually go as high as 1u BID, and sometimes recommend .5u BID. I thought that was odd when I read the study.
And then the "go slow" part of the equation. We usually tell people to increase or decrease dose in .25 (or as high as .5) unit increments. In this study, adjustements were made in increments as high as 1u at a time.
So the study didn't follow the FDMB "standard" start-low, go-slow approach.
The other thing that bothered me was that of the 3 insulins, lantus is the only one we would recommend. PZI Vet is no longer available, and Vetsulin/Caninsulin is always recommended against when newmems show up saying they are using it. It would be awesome if Levemir and Prozinc (which is not the same as PZI, old or new) were used instead.
What I did like about the study was the absence of any Tight Regulation mention. The cats were dosed 12 hours apart, even amounts AM and PM. The only mention of BG results were at pre-shot and at nadir, outside of the first 3 days on insulin when all cats were tested every two hours. After the three day period, the cats were sent home with a set dose, and told to come back a week later for another test. If needed, based on preshot and nadir numbers after a 12 hour curve, the dose was adjusted and kitty went home with a new dose for another week. This continued every two weeks from that point on. A fructosamine test was run every four weeks. So it sounds like the only time BG was checked was during the weekly or bi-weekly vet visits when a 12 hour curve, testing every two hours, was done.
The info on food intake was sort of vague:
food intake was not restricted for any cat during
the first 2 weeks of insulin therapy. Dietary energy restriction was recommended after 2 weeks for cats with
body condition scores of 7 or above (on 1e9 scale).
It doesn't say at what time of day they ate, or how much, just that it was controlled after the first two weeks.
It also said that if the preshots on curve days were below 216, then if it stayed that low over the 12 hour period, the cat was sent home with no insulin and rechecked to see if it stayed that low. I think the term they used was "suspected of being in remission"
After a minimum of 2 weeks of insulin therapy, if the
pre-insulin blood glucose concentration was less than
12 mmol/l, insulin was withheld and serial blood glucose measurements were continued for 12 h to determine if the cat was no longer insulin dependent and
thus in remission. Cats suspected of being in remission were discharged from hospital without insulin
treatment and had their blood glucose concentration
measured weekly for 3 months, to confirm remission.
So their definition of "remission" and ours are a little bit different.
Cats also got a dose reduction if their preshots were below 250 or their nadir was below 126, and the reduction was .5u, which also sounded unfamiliar, both the numbers and the fact that reductions were given based on either preshots or nadirs.
End results -
100% of the lantus cats went into remission within 16 weeks.
25% of the caninsulin cats went into remission.
38% of the PZI cats went into remission.
There were zero lantus cats who went hypo (no clinical signs even though some of their numbers were considered hypoglycemic), but two of the Caninsulin cats, and one PZI cat did go hypo and required IV glucose treatment to bring them back up.
Based on the end results, and knowing that all the lantus cats went into remission without using TR, I'd have no problem using or recommending Lantus in the future. I do wish, however, they would do another study that included Prozinc and Levemir so we'd have good data on the three most common insulin types used now.
Carl
