Insulin glargine
Insulin glargine is a new long-acting synthetic insulin analogue that has shown encouraging results in recent clinical studies. After subcutaneous injection in humans, this insulin forms a microprecipitate in the subcutaneous tissue and is slowly released throughout the day with no pronounced peak effect (so-called ÒpeaklessÓ insulin). In healthy cats, a peak occurs at 16 hrs with significant glucose suppression for up to 24 hrs. When using glargine in diabetic cats, most cats may be maintained on once daily injections of glargine, but superior glucose control is achieved if the insulin is given twice daily. The starting dose is 0.25 to 0.5 U/kg given twice daily.

A recent clinical study showed that treatment with glargine results in higher remission rates than PZI and Lente insulins in diabetic cats. Twenty-four newly diagnosed diabetic cats were divided into 3 groups and treated with either glargine, PZI, or Lente insulin, and fed a low carbohydrate, high protein diet (Purina DMª canned). Insulin was initially given at 0.5 U/kg SQ , if the blood glucose was > 360 mg/dL, and 0.25 U/kg if the blood glucose was < 360 mg/dL. Insulin dose was then adjusted based on serial glucose curves and water intake. At diagnosis, there was no statistical difference between treatment groups with regard to age, body condition score, body weight, and initial fructosamine concentrations.

Mean 12-hr glucose concentrations at 4 wks was significantly lower for the glargine treated cats (239 mg/dL) than the PZI and Lente (343 mg/dL and 553 mg/dL, respectively). Fructosamine concentrations were also significantly lower than at diagnosis for the glargine treated cats (343 and 553 umol/L) but not for the PZI (469 and 570 umol/L) or Lente (465 and 574 umol/L) groups.

All 8 cats treated with glargine went into diabetic remission within 4 mo of starting treatment, while 3 cats treated with PZI and 2 cats treated with Lente went into diabetic remission. Of the 7 cats treated with glargine that are still alive, 6 remain in remission (mean remission time 13 ± 3.5 mo). No cats in the glargine treated group developed clinical hypoglycemia. It is believed that improved glycemic control with glargine resulted in better reversal of B-cell glucose toxicity and higher diabetic remission.

Most dogs can be managed successfully with human NPH or Lente insulin. The advantage of Lente over NPH is a more consistent duration of action. For example, in some patients the duration of action of NPH can be as short as 8 hrs. The new porcine Lente (Vetsulin™ Intervet) is now available as a U-40 preparation. The theorectical advantage of this insulin in dogs is the identical structure of porcine insulin and dog insulin, although past studies in normal dogs have shown that porcine and human Lente have similar pharmacokinetic properties. This insulin may prove advantageous for treating small dogs, where accurate dosing of small amounts of insulin are required for dogs with poor glycemic control from being treated with NPH or Lente. The starting dose of insulin, whether Lente or NPH, is 0.25 to 0.5 U/kg given twice daily.

Reference: Marshall and Rand, JVIM abstract;19:425, 2005.