Q & A: Diabetic Cat on Compounded Insulin

I would like your advice on the use of compounded insulin. My patient is a 3.8 kg, 15-year old male diabetic cat that has been on compounded PZI insulin for the past 2 years.

Until recently, he was doing fine on 4 units of the PZI twice daily. However, the cat suddenly developed a severe hypoglycemic episode, which required a 2-day hospitalization stay for treatment at our emergency clinic. The owners brought him directly from the emergency clinic to my hospital; he is bright and alert, but the blood glucose concentration is now high at 458 mg/dl (normal < 150 mg/dl).   

So insulin therapy is being re-started, but I feel this cat should be on ProZinc, not the compounded PZI product. What would be in the best interest for this cat?  If I switch this cat from the compounded insulin, how do I go about it?

My Response:

ProZinc Insulin

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.

In addition to the ProZinc, I'd recommend a good canned cat food — one with a composition that is low in carbohydrates (<10% of calories) and higher in protein (>40% of calories). By lessening the insulin resistance that is a hallmark of diabetes in cats, that diet change will make cats more sensitive to the effects of insulin. What are the owners feeding him now?

Follow-up:

His diet consists of dry Science Diet and Canned Friskies cat food. Are these diets acceptable? Do you think Hill's m/d would be a better choice?

My Response:

In my opinion, m/d is too high in carbohydrates for a diabetic cat.  A better prescription diet food is Purina DM. However, most of my diabetic cats are doing well on an over-the-counter canned food that are low enough in carbohydrates and high in protein content. It may be that the canned Friskies food that your patient is eating now is completely acceptable.

Check out this website (http://binkyspage.tripod.com/foodfaq.html), which gives you a breakdown of the composition of the various prescription and over-the-counter diets. It turns out that many of the over-the-counter diets have a better composition of protein and carbohydrates than you might have thought — even better than many of the more expensive prescription diets. Very few of my diabetic cat patients require a prescription diet to fulfill their nutritional needs.

As I discussed in other posts on diet management, almost all dry food cat diets are much too high in carbohydrates and  too low in protein content. That is why I believe it's best to limit the amount of dry food that is fed to diabetic cats, or even better, not feed dry food at all.

References:

1. Nelson RW, Henley K, Cole C, et al. Field safety and efficacy of protamine zinc recombinant human insulin for treatment of diabetes mellitus in cats. Journal of Veterinary Internal Medicine 2009;23:787-793.
2. Scott-Moncrieff, JC. Comparison of the characteristics of PZI insulin obtained from different commercial sources. J Am Vet Med Assoc 2011 (in press)
3. Rucinsky R, Cook A, Haley S, Nelson R, Zoran DL, Poundstone M. AAHA diabetes management guidelines for dogs and cats. Journal of the American Animal Hospital Association 2010;46:215-224.
4. Frank G, Anderson W, Pazak H, Hodgkins E, Ballam J, Laflamme D. Use of a high-protein diet in the management of feline diabetes mellitus. Veterinary Therapeutics 2001;2:238-246.
5. Rand JS, Fleeman LM, Farrow HA, Appleton DJ, Lederer R. Canine and feline diabetes mellitus: nature or nurture? The Journal of 2004;134(8 Suppl):2072S-2080S.