Update on Insulin Glargine use in Diabetic Cats
Jacquie Rand BVSc DVSc Dip ACVIM*, Rhett Marshall BVSc, MACVS*#,
*Centre for Companion Animal Health, School of Veterinary Science
The usefulness of glargine for treating newly diagnosed diabetic cats has been evaluated and is presented in an abstract at this forum5. Twenty-four newly diagnosed diabetic cats (17m,7f) were treated with either glargine, PZI or lente (n=8 for each group) and fed a very low carbohydrate-high protein diet (Purina DM canned). Insulin was initially given at 0.5U/kg BID S/C if blood glucose was >360mg/dl, and 0.25U/kg BID S/C if blood glucose was <360mg/dl. Insulin dose was then adjusted based on serial blood glucose curves and water intake. Cats were defined as achieving diabetic remission if normoglycemia was maintained without insulin therapy for more than 2 weeks.
At diagnosis, there was no statistical difference between treatment groups for age, body weight, body condition score, or concentrations of fructosamine, blood glucose, B-hydroxybutyrate or bicarbonate. Four of 8 cats in each group were Burmese5.
There was a non-significant trend for glargine treated cats to have lower 12hr glucose concentrations after 10 and 17 days, than those treated with PZI or lente 5. Mean 12hr blood glucose at 4 weeks was significantly lower for glargine than PZI and lente treated cats. Fructosamine concentration after 4 weeks of treatment was significantly lower than at diagnosis for glargine treated cats but not for PZI or lente5.
All 8 cats treated with glargine went into diabetic remission within 4 months of beginning treatment, while 3 cats treated with PZI and 2 cats treated with lente achieved diabetic remission5. Of the seven glargine treated cats alive, six cats remain in remission at the time of publication (mean remission time=13+3.5 months) 5. One of the remaining two cats alive treated with PZI (mean remission time=8.3+3.3 months) and both cats treated with lente (mean remission time=8+2 months) remain in remission5.
Only 1 cat treated with glargine required an increase in insulin dose above 0.5U/kg BID, and 7 of 8 cats had their insulin dose reduced in the first 3 days of treatment. This is an important factor when initiating treatment with glargine, as there is usually a carry-over effect from the previous dose that may take several days to become apparent.
A significant finding in this trial was that no cat treated with glargine showed clinical hypoglycemia despite having biochemical hypoglycemia, while 2 cats treated with lente and 1 cat treated with PZI insulin exhibited signs of clinical hypoglycemia.
Glargine can be safely instituted at 0.5U/kg bid and serial blood glucose curves should be obtained daily for 3 days either in hospital or at home. When evaluating the blood glucose curve using glargine, it is often more useful to assess pre-insulin glucose concentration rather than the nadir glucose. We have found it often takes 3-5 days for a good glucose-lowering effect to be seen in the glucose curves, possibly because of the long duration of action and carry-over effect of glargine. Almost all cats will need to have their initial dose reduced within 2 weeks and many will achieve remission within 4 weeks 5
Monitoring and adjusting insulin dose when using glargine should be based on a number of parameters including; pre-insulin and nadir glucose conc, water intake, urine glucose concentration and clinical assessment as shown in Table 1. We have found pre-insulin glucose concentrations measured at home an excellent tool for well-educated owners to safely modify daily doses of glargine. Cats treated with glargine should have a negative, 1+ or 2+ urine glucose (scale 0-4+) and a value of 3+ or 4+ likely indicates that a dose increase is required.
The good glycemic control when using glargine likely reverses glucose toxicity of the B-cells, which facilitates endogenous insulin production and a reduced requirement for exogenous administration. Insulin dose may be reduced sequentially as indicated by blood glucose concentration, urine glucose and water intake until the dose is 1U SID. Even if normoglycemic, it is recommended that insulin is not withdrawn within 2 weeks of commencent of therapy. Sequential deduction of insulin dose to 1 U SID is recommended before insulin is withdrawn, and the cat carefully monitored afterwards to ensure remission has continued. It is also imperative that cats remain on a low-carbohydrate diet with calorie control to prolong the remission period. It is the authors’ experience that newly diagnosed diabetic cats that have good glycemic control within the first few weeks of therapy, are very likely to go into diabetic remission. Cats that have been long-term diabetics are less likely to go into remission probably because of progressive B-cell loss.
It is the authors’ conclusion that glargine is safe and effective in treating feline diabetes and should be the preferred insulin in newly diagnosed diabetic cats. Long-term diabetic cats should be changed to glargine if there is poor glycemic control or owners wish to pursue once daily injections. High remission rates are expected in newly diagnosed cats when combined with a low-carbohydrate diet.
