Changes: PZI

Revision as of 17:12, 6 November 2006

Felineinsulin8 — Feline insulin compared to Bovine, Porcine and Human versions. Up to 4 amino acids differ. The closest match to feline is bovine with only one amino acid difference; the least close is human with four amino acid differences^[1].

Various types of veterinary insulins are known as PZI, "Protamine Zinc Insulin" . The ones we use most often for animals are a combination pork/beef-derived insulin or a beef-derived insulin. Because most are veterinary insulins, PZIs are not available at normal human pharmacies.

The only PZI insulin still available for people is CP Pharma's Hypurin Bovine Protamine Zinc and it must be imported from the UK.

PZI veterinary insulins are intermediate-acting to long-acting, and can be closer in molecular structure to a cat or dog's own insulin than human-type or analog insulins. PZI is rarely used in dogs but is considered when other insulins are not effective^[2].

Antech Diagnostics' newsletter^[3] mentions a JAVMA 2001 study^[4] in which 75% of previously treated hard-to-regulate cats did well with the insulin. It went on to say that most cats do require PZI twice daily. The other 25% of tested cats did not reach peak with PZI insulin until 9 hours + after injection; they would likely be able to use only one shot per day. As the study illustrates, absorption, peak and duration of PZI is variable.

PZI itself was introduced in 1936; it was the first insulin having any type of suspension. Before PZI, the only insulin available was R/Neutral, having no additives to alter or extend its action. Until then, many with diabetes had to get up during the night to take an insulin injection because R/Neutral did not last long enough for an uninterrupted night's sleep^[5] .

Technical details

PZI contains more zinc and protamine than NPH/isophane insulin and it is primarily the extra protamine which gives it its long-acting duration. The additional protamine in the suspension^[6] must first be broken down by proteolytic enzymes AKA proteases^[7], before the insulin in PZI can be absorbed. NPH/isophane insulin contains less protamine than PZI does and because there's less, it is an intermediate-acting insulin.

Types of Veterinary PZI

Manufactured

These are manufactured, not compounded, insulins. This means the insulin keeps longer, and is less likely to vary, as compounded insulins can, from batch to batch. The manufactured insulins have a shelf life of three years (unopened).

PZI Vet (IDEXX)

25934-1 — PZI Vet by IDEXX-a U40, 90% beef, 10% pork protamine zinc insulin.

PZI Vet is made by IDEXX Laboratories (formerly Blue Ridge). PZI Vet is a beef/pork PZI insulin commonly used in diabetic cats in the U.S. Some compounding pharmacies may refer to their PZI insulins as PZI Vet, but you aren't using PZI Vet^[8] unless it is made by IDEXX Labs. Unlike the other PZI's below, PZI Vet is a mix of beef and pork insulin. Beef insulin is closest to a cat's own insulin, and pork is identical to a dog's. PZI Vet is a manufactured insulin; the formula is that of Lilly's 90% beef/ 10% pork Iletin I Protamine Zinc insulin; Blue Ridge purchased it from Eli Lilly after the firm discontinued it.

Insuvet PZI

91 main — Insuvet Protamine Zinc--pure beef U100 PZI insulin.

Insuvet Protamine Zinc or Insuvet PZI is a PZI from Insuvet, similar to BCP's PZI above. Insuvet also makes two other veterinary insulins.

Schering-Plough Animal Health contracts CP Pharma to produce its Insuvet line of bovine insulins^[9]. Some UK pet pharmacies offer both the Insuvet-branded and the Hypurin-branded insulins. The only difference here may be pricing.

Insuvet insulins are only available in the UK; the option for those in other countries is either importing from CP Pharma or, if you are in North America, the compounded PZI in various strengths available from BCP and VPOA (US) and Summit (Canada).

CP Pharma

69 main — Hypurin Bovine Protamine Zinc-U100 all-beef PZI insulin.

Hypurin Bovine Protamine Zinc is a U100 100% bovine PZI manufactured by CP Pharma. It is approved for use in humans and can be imported into the US and other countries.

CP Pharma also produces Hypurin Vet Protamine Zinc, which is pure beef but not offered outside of the UK.

Those CP Pharma insulins are comparable to Insuvet Protamine Zinc, made by Schering-Plough Animal Health, a U100, 100% bovine PZI for veterinary use that is only available in the UK.

CP Pharma actually produces the Schering-Plough Animal Health Insuvet insulins^[10].

Importing-Canada

Your vet may also be able to obtain manufactured PZI insulin for you through Health Canada's Emergency Drug Release program^[11]. With it, you are able to receive up to 6 months worth of insulin; a C$ 50.00 fee for the application is required ^[12]. If permitted, you would then be eligible to import PZI insulins such as PZI Vet,Insuvet Protamine Zinc, Hypurin Vet Protamine Zinc, or Hypurin Bovine Protamine Zinc, as well as the other insulins Insuvet and CP Pharma produce.

The program is similar to Health Canada's Special Access Programme ^[13] for importing necessary drugs for people.

Compounded

BCP PZI

BCP PZI is a bovine-origin PZI-based insulin. Because it's beef based, its amino acid chain is almost the same as that of a cat, so it's especially well-matched to cats.

BCP Veterinary Pharmacy^[14] in Houston, TX, USA, manufactures and is the sole source supplier for BCP PZI. BCP PZI is commonly used in diabetic cats in the U.S. BCP PZI is a compounded insulin.

VPOA PZI

All-Beef 40U PZI insulin is available from Veterinary Pharmacies of America in Houston, Texas, a source recommended by Dr. E. Hodgkins.^[15]

BCP, VPOA, and other compounding pharmacies are the only US source for pure beef insulin of any type. Manufactured beef insulins must be imported from CP Pharma.

UK, Canada, and US-other compounded PZIs

Those in Canada can obtain 100% beef compounded PZI in U100 strength from Summit Veterinary Pharmacy^[16] in Ontario. Summit sells their insulin solely through vets--yours will need to place the order for you.

Summit's insulin is comparable to BCP's U100 strength all-beef PZI, Insuvet Protamine Zinc, and the Hypurin Bovine Protamine Zinc and Hypurin Vet Protamine Zinc insulins of CP Pharma.

There are also pharmacies in the US and UK that compound PZI based on human ("regular") or animal-source insulins. This link^[17] and this one^[18] list some of those compounding pharmacies, their contact information, and prices for their insulins.

Handling and use

According to Merck^[19], in cases where a shorter-acting insulin is needed in addition to the PZI, the protamine zinc insulin must always be injected separately--NO mixing--due to the excess of protamine in the insulin formula^[20]^[21].

Specifications of PZI

British National Formulary defines protamine zinc insulin as a sterile suspension of insulin in the form of a complex obtained by the addition of a suitable protamine and zinc chloride.

British Pharmacoepia (BP) and United States Pharmacoepia (USP) definitions^[22]^[23]:

Protamine Zinc Insulin

Sterile buffered suspension of mammalian insulin to which protamine and zinc chloride are added. White suspension. pH 6.9 - 7.5 iso-osmotic with blood. Contains for each 100 units of insulin, 1 - 1.7 mg of protamine sulphate and zinc chloride equivalent to 200 per g of zinc, 10 - 11 mg of sodium phosphate.