I had a chat with my vet last month, and she has always (since it became available) prescribed compounded bovine PZI (that's what Bob had). There were two major sources for it. BCP and VPA labs, both in Texas. There were also smaller labs that made and sold it.
A couple of months ago, she said she had to switch to Prozinc (the rDNA insulin). VPA was the place she had always sent her clients to to buy it, and she could no longer get it from them. It was rarely available from BCP, so rather than have her clients not be able to get insulin when they needed it, she decided to use Prozinc instead. Several people here, and she, have said that it has become hard to get Prozinc now because it is "always on back-order".
My guess is that with the old compounded PZI being harder and harder to find, many vets are doing the same thing my vet did, and because of that, Prozinc from Boehringer can't keep up with the orders?
Now, it appears that there are also
compounded human rDNA versions of "PZI" available. They can't call it "Prozinc" because that is the name that Boehringer sells theirs under.
So, there are two completely different compounded insulins available (although I think the bovine type is just about gone from the market). After reading what I've read tonight, I think I would stay away from any form of compounded PZI. The problem with compounding in general is consistency in product quality. I'm going to include a couple of links.
This is the information from Wedgewood. They make a compounded human rDNA version of PZI
http://www.wedgewoodpetrx.com/learn...amine-zinc-insulin-pzi-for-dogs-and-cats.html
The PZI described on this page is compounded with recombinant human insulin. PZI was recently approved by the FDA for use in cats. When the appropriate form or dose of this drug is not available through a veterinary pharmaceutical manufacturer, it may be compounded by a specialty pharmacy. PZI is also used to treat diabetes in dogs and is considered accepted practice in veterinary medicine.
These links are pages by Dr. Mark Peterson, and he explains the difference between the Boehringer product and the newer compounded products and why they are inferior:
http://endocrinevet.blogspot.com/2011/09/q-diabetic-cat-on-compounded-insulin.html
I could not agree more about switching to ProZinc, the PZI insulin FDA-approved for use in cats (1). I do not recommend ever using compounded PZI products because of the fact that potency can vary greatly from batch to batch (2). It's difficult enough to regulate a diabetic cat without the additional variable of the insulin changing its potency every time the owner buys a new bottle. I feel that it’s far better to get manufactured insulin that has external quality control standards applied to it.
As far as the transition from compounded PZI to ProZinc, I would recommend dropping the ProZinc dose back down to 2 units BID. Then I'd wait a weeks and make additional dose adjustments based upon the cat's clinical status (activity, appetite, water consumption and urination) and a glucose curve, if you feel it's necessary.
What I found nice was that this vet has a link to "Binky's Page" there.
http://endocrinevet.blogspot.com/2012/06/characteristics-of-commercially.html (this was published just last month)
Currently, an FDA-approved human recombinant PZI product (ProZinc, Boehringer Ingelheim Vetmedica, Inc.)
http://www.prozinc.us/) is commercially available for use in cats and has been reported to result in clinical responses comparable to those achieved with PZI of bovine and porcine origin (2,3). Because of the high cost of commercially manufactured PZI, alternative products have been made available to veterinarians by compounding pharmacies.
The purpose of this study by Scott-Moncrieff et al (7) was to evaluate the quality and consistency of several compounded PZI products and compare them to the commercially manufactured PZI insulin. Moreover, this study was designed to determine if compounded PZI would be as reliable as the commercially manufactured PZI product.
What I can't find anywhere is a list of the 12 labs that the compounded products were made in.
My Bottom Line:
Protamine zinc insulin is a complex protein, requiring special expertise to manufacture. The long duration of PZI is attributable to the complexing of insulin with zinc and protamine in precise proportions to form a precipitate, which is released slowly from the subcutaneous tissues after injection (5,6).
It is easy to imagine why a compounding pharmacy may not be able to manufacture PZI insulin, especially insulin that is safe to use and consistent in concentration, onset of action, and duration of the insulin effect. To be honest, I find it more amazed that a compounding pharmacy could produce an insulin product that worked at all!
However, in this study by Scott-Moncrieff (7), a number problems were identified in compounded PZI preparations, included the following:
Lack of an expiration date or lot number on the vial
Lack of identification of the species of origin (bovine, porcine, or human)
High endotoxin concentration
pH below or above the recommended range
Low total insulin concentration
Zinc concentrations below or above acceptable limits
Variability in insulin concentration among vials from a single compounding pharmacy
Variability in insulin concentration among different compounding pharmacies that had the same labeled concentration
Unacceptably high concentrations of insulin in the supernatant.
This study was not designed to identify the clinical consequences of these problems with the use of compounded PZI insulin in cats. However, such deficiencies would likely contribute to poor glycemic control in cats treated with compounded PZI. Other problems that may be seen would include changes in the onset and duration of insulin action, hypoglycemia due to inadvertent insulin overdosage, or fever due to endotoxin.
Based on the results of this study (7), it is clear that compounded PZI insulin cannot be recommended. Regulating diabetic animals is difficult enough without having to deal with variations in insulin quality and potency every time we buy a new bottle. I believe that it’s best to use a FDA-approved insulin preparation that has external quality control standards applied to it.
Remember, a bad insulin is almost worse than no insulin at all.
I think I'd stay away from compounded products, and I'm really glad that I only had to buy it once, so I didn't have to worry about batch consistency while I was given bovine compounded PZI to Bob.
Carl
