Life of the Lintee Bean

So, your cat is diabetic and you’re wondering which insulin you should be using to get those nasty blood sugar levels down (hopefully permanently so your cat can be managed on diet alone!)

My personal preference is PZI (protamine zinc insulin).  It’s duration is a little over 12 hours, which works well for a twice-daily dosing schedule.  (We WANT some overlap between doses, so we’re not dealing with very high blood sugar levels caused by no insulin being in effect.)   Once my supply of PZI-Vet by Idexx is exhausted, I’ll use a compounded PZI by BCP or Veterinary Pharmacies of America (VPA).  I’ve used BCP-PZI before with success – I noticed no difference between it and the PZI-Vet (except the lower cost).  As I’ve noted in the past, PZI-Vet by Idexx has been discontinued but that does NOT mean PZI is not available!  Compounded PZI is still available for use.

Louie says "PZI works for me!"

There is a study by Dr. Rand claiming higher remission rates with Lantus/Glargine than other insulins – where this study is flawed, in my opinion, is that it compared Dr. Rand’s tight regulation protocol for Lantus to similar dosing of the other insulins – but not necessarily a tight regulation protocol for those insulins.  Dr. Hodgkins sees rates of remission just as high as Dr. Rand’s using Dr. Hodgkins’ tight regulation protocol for PZI.

If I couldn’t use PZI – my next choice would be Lantus (Glargine) or Levemir – but as long as PZI is available I’ll stick with it.  It’s worked very well for the nine diabetic cats (adopted and fostered) I’ve treated, so I see no need to fix what isn’t broken.  Plus, Lantus is a lot more fragile than PZI (and I’m clumsy with a tendency to drop things or shake things or forget and insert a little insulin from the syringe back into the vial because I drew up too much).  Lantus and Levemir also appear more expensive than PZI – and seem less predictable.  The caregivers I know using Levemir generally use short-acting boosters as Levemir has such a long onset (time until it starts working) which adds a complexity (and fear, as short-acting insulins can drop blood sugar levels quickly and harshly) I really don’t want to deal with.

I’d only use Vetsulin/Caninsulin if, for some unforseeable reason, PZI, Lantus, and Levemir weren’t available.  From what I have seen in studies, anectdotal evidence on message boards, and articles – Vetsulin is much harsher acting (drops blood sugar levels quickly) and does not last nearly as long as PZI, Lantus, or Levemir.  Vetsulin (also known as Caninsulin, as it was developed for use in canines/dogs) is what is known as a “lente” insulin and has a quicker onset and shorter duration than the longer-acting insulins of PZI, Lantus, or Levemir.  Just because Vetsulin is now FDA-approved for use in cats, does NOT mean it is the best option for diabetic cats!

 From the Vetsulin patient information sheet:

ADVERSE REACTIONS

Cats

In a field effectiveness and safety study, safety data was reported for 78 cats receiving vetsulin®. Hypoglycemia (defined as blood glucose <50 mg/dL) was reported in 61 cats (88 total incidences). Fifteen of the occurrences (involving 13 cats) were associated with clinical signs described as lethargy, diarrhea, decreased appetite/anorexia, vomiting, and hypothermia. One cat had seizures following accidental overdosing by the owner and again during the subsequent dose adjustment period. The cat responded to supportive therapy and had no further hypoglycemic episodes. In all cases of hypoglycemia, the clinical signs resolved following symptomatic treatment and/or dose adjustment.

Polyneuropathy was reported in 4 cats. Two injection site reactions were reported: one as a mildly thickened subcutaneous tissue reaction and the second as a mild bruising. The following clinical observations occurred in the field study following treatment with vetsulin® and may be directly attributed to the drug or may be secondary to the diabetic state or other underlying conditions in the cats: vomiting, lethargy, diarrhea, decreased appetite/anorexia, pancreatitis, dermal events, respiratory disease, urinary tract disorder, renal disease, dehydration, weight loss, polydipsia, polyuria, behavioral change, and ocular discharge/conjunctivitis.

In a smaller field effectiveness and safety study, 14 cats were treated with vetsulin®. Hypoglycemia was reported in 6 cats (8 total occurrences). Lethargy not associated with hypoglycemia was reported in 4 cats (6 total occurrences). The following clinical observations occurred in the field study following treatment with vetsulin® and may be directly attributed to the drug or may be secondary to the diabetic state or other underlying conditions in the cats: foul odor to stool, diarrhea, dull coat, rapid, shallow breathing, stiff gate in rear, gallop rhythm, and pruritus with alopecia.

During the 1998-2007 period, the following adverse events in 50 cats treated with porcine insulin zinc suspension were reported to Intervet International and Intervet Inc.:  Death, seizures, lack of effectiveness/dysregulation, hypoglycemia, allergic or skin reaction, lethargy, vomiting/diarrhea, injection pain, hyperthermia, nystagmus, PU/PD, and abnormal behavior.

GENERAL PHARMACOLOGY

Porcine insulin is similar in amino acid structure to canine insulin.

That’s an awful high hypoglycemia rate, isn’t it? 61 out of 78 cats and 6 out of 14 cats?  Also, why would I want an insulin similar to canine insulin – when PZI is most similar to FELINE insulin?

For more information on feline diabetes, visit Feline Outreach.

Other references and resources:

Drat: That Diabetic Cat!  Getting a better grip on those hyperglycemic felines

Protocol for Success in Managing Feline Diabetes

The latest management recommendations for cats and dogs with nonketotic diabetes mellitus

Why not look at the recent study “Glargine and protamine zinc insulin have a longer duration of action and result in lower mean daily glucose concentrations than lente insulin in healthy cats”?  Because it was performed on nine NON-DIABETIC cats.  While the information is interesting, and I agree Glargine/Lantus and PZI have longer duration of action than a lente insulin such as Vetsulin/Caninsulin, I’m much more interested in how insulin acts in DIABETIC cats.