Clinical Study to Evaluate a New Formulation of Protamine Zinc Insulin for Treatment of Diabetes Mellitus in Cats
ACVIM 2008
G.D. Norsworthy1; R.C. Lynn2
Alamo Feline Health Center, San Antonio, TX, USA; IDEXX Pharmaceuticals, Inc.
Greensboro, NC, USA

Treatment of diabetes mellitus (DM) in cats usually requires administration of exogenous insulin. Protamine zinc insulin (PZI VET® Insulin, IDEXX Pharmaceuticals, Inc.) is a long acting beef-pork insulin that is manufactured using pancreatic glands harvested at slaughter. PZI VET insulin is known to be effective in treating cats with DM. Unpublished work in rats with DM showed that a new protamine zinc formulation based on recombinant insulin (PZIR) provided glycemic control that was similar in duration and potency to PZI VET insulin. The purpose of this study was to compare the clinical efficacy of PZIR to that of PZI VET in pet cats with DM.

Fifty (50) pet cats with DM that had stable glycemic control on PZI VET insulin were selected for the study. On Day 0 of the study all cats were switched from PZI VET to PZIR after they were examined and weighed and had blood collected for serum fructosamine. The PZIR was administered at the same dose and dose interval as PZI VET. Cat owners were instructed to make no other changes in the daily diet or routine. Body weight, insulin dose, and serum fructosamine were rechecked on Day 15 and Day 30. Subjective owner impression of the cat's response to therapy was recorded during the 30-day period. On Day 30, the cats were switched back to PZI VET at the same dose as PZIR.

Forty-seven (47) of the 50 cats finished the 30-day study. Three cats were removed from the study; 1 cat went into diabetic remission, 1 cat became fractious, and 1 cat became hypoglycemic. In the remaining 47 cats there were no significant differences in insulin dose, body weight or serum fructosamine at Day 15 or Day 30 when compared to Day 0. PZIR was given twice daily.

Time point

Body weight


Insulin dose

Day 0

13.8 ±2.8

445 ±91

4.2 ±3.5

Day 15

13.8 ±2.9

446 ±95

4.4 ±3.4

Day 30

13.7 ±2.8

432 ±91


Other than one cat with hypoglycemia (mentioned above) and one cat with hyperglycemia, there were no adverse reactions attributable to PZIR. Cat owner observations were consistent with satisfactory glycemic control and our clinical experience with the use of PZI VET insulin for cats with DM.

The results of this study in pet cats are similar to the previous findings in rats with DM. This study in diabetic cats also demonstrates that protamine zinc insulin based on recombinant insulin (PZIR) provides glycemic control that is comparable to that of PZI VET insulin at the same dose and dose interval.

Speaker Information
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Gary Norsworthy

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