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Pharmacotherapy Options in the Treatment of Feline and Canine Diabetes

Janine Manning, Pharm.D. Candidate 2011

Lake Erie College of Osteopathic Medicine, School of Pharmacy

As healthcare professionals, we have seen the increase in the occurrence of diabetes mellitus detected over the past decade in the human population. This has lead to treatment advances to help reduce diabetic complications. What we may not encounter as often are these healthcare issues in the feline and canine populations, which may ultimately lead to feline neuropathy or canine cataract formation if left untreated. To play a valuable role in helping to prevent these long-term health complications, we need to understand the pathophysiology of animal diabetes, the frequency of administration and dosing of different types of insulin, and proper monitoring in these populations.

 
Pathophysiology

JManningT-1

Diabetes mellitus results from a decrease in or lack of pancreatic beta cell function leading to altered insulin secretion and presence of clinical manifestations (Table 1). In canines, this may result from antibody destruction of beta cells, genetics, or pancreatic inflammation causing type I, insulin dependent diabetes. In feline species, decreased beta cell function from insulin resistance, genetics, or pancreatic inflammation leads to type 2, non-insulin dependent diabetes. The main differences of the disease in cats and dogs is the manifestation of stress hyperglycemia in cats, causing a transient elevation in blood glucose levels, and the occurrence of diabetic remission in cats allowing for discontinuation of insulin.

Treatment
 
Table 2. Insulin Frequency and Dosing
Lantus
ProZinc

Initial dose

BG > 360mg/dL = 0.5 units/kg every 12 h

BG < 360mg/dL = 0.25 units/kg every 12 h

Initial dose – 0.25 units/kg every 12 h (not to exceed 1 unit/ injection)

Regular regimen – 0.5 units/kg every 12 h

Vetsulin
Humulin NPH

Initial dose – 0.25 units/kg every 12 h

Regular regimen – 0.5 units/kg every 12 h

Initial dose – 0.25 units/kg every 12 h

Regular regimen – 0.5 units/kg every 12 h

 Feline diabetes mellitus is based on blood glucose >250 mg/dL, along with clinical manifestations (Table 1). Insulin should target blood glucose (BG) levels of 100-300 mg/dL. Insulin used for the initial treatment of DM in cats includes Lantus (U-100 insulin glargine) or ProZinc (U-40 protamine zinc recombinant human insulin).

Canine diabetes mellitus is based on blood glucose >200mg/dL, along with clinical manifestations (Table 1). Targeted BG concentrations are 100-250 mg/dL. Vetsulin (U-40 porcine zinc insulin suspension) or Humulin NPH has been recommended in canine diabetes. All treatments are initiated at a low dose to assess initial BG effects (Table 2). Levels less than 80mg/dL in cats requires a reduction in insulin dose by 50% or dose omission until glycosuria returns. A reduction in dose of 25% is recommended for dogs.

According to the FDA Center for Veterinary Medicine, Vetsulin has been found to contain unpredictable amounts of crystalline zinc resulting in variable duration of action. Other insulin products have been recommended due to this finding. Humulin NPH may be the current insulin of choice for controlling canine hyperglycemia. A recent study performed by Palm CA, et al. showed adequate reductions in blood glucose levels following the administration of < 1 unit/kg Humulin NPH twice daily in 10 diabetic dogs.  

Monitoring

Cats or dogs may not always show clinical signs of hypoglycemia until blood glucose levels are low enough to cause seizures or coma. To avoid hypoglycemia, it is pertinent that home monitoring is performed and insulin doses not be increased without veterinarian supervision. At home BG monitoring is an important measurement tool to determine effectiveness of glucose lowering. It may also solve the issue of stress hyperglycemia of cats being taken to the clinic. BG levels are measured every 2-3 hours after ProZinc or every 4 hours after Lantus administration for 10-12 hours. Testing urine for glycosuria and ketonuria periodically is also recommended at home. A daily log with the following should be kept for cats and dogs:

  • Food and water intake
  • Appetite
  • Insulin dose
  • Weight
  • Symptoms of hypoglycemia (weakness, lethargy, bumping into things, BG < 80 mg/dL)

JManningG-2A blood glucose curve (BGC) may be obtained in the veterinary office or at home if diabetes symptoms persist, hypoglycemia occurs, upon initiation of insulin in dogs or after a dose adjustment. BGC testing requires levels be drawn every 2 hours for a total of 12 hours following administration of insulin. An appropriate BG curve (Graph 3) is a good indicator of appropriate dosing. Ineffective BG lowering (Graph 4) may be due to inadequate insulin dosing or stress hyperglycemia (cats). The nadir on a BGC should be 80-150 mg/dL ideally and should occur 8 hours after short acting or 12 hours after long acting insulin administration. Measurement of fructosamine may show elevation in glucose levels over a 2-3 week if the value is elevated. The veterinarian also performs this test.

Ultimately, feline and canine diabetes mellitus can lead to long-term complications such as neuropathy (cats) or cataracts (dogs) without appropriate medical treatment. In order to prevent these complications, it is important to know how to treat these conditions appropriately and stay current regarding the treatment updates and monitoring techniques discussed.

 
 
 
 
 
 
  
 
References
  1. Rucinsky R, Cook A, Haley S, et al. AAHA diabetes management guidelines for dogs and cats. Journal of the American Animal Hospital Association. 2010;46:215-24.
  2. Bennett N. Monitoring techniques for diabetes mellitus in the dog and cat. Clinical Techniques in Small Animal Practice. 2002;17(2):65-69.
  3. Behrend EN. Update on drugs used to treat endocrine diseases in small animals. Vet Clin Small Anim. 2006;36:1087-1105.
  4. FDAÒ – U.S. Food and Drug Administration. Rockville, MD: Center for Veterinary Medicine; 2010. http://www.fda.gov/AnimalVeterinary/NewsEvents/CVMUpdates/ ucm188752.htm. Accessed January 11, 2011.
  5. Canine Diabetes Web site. http://www.caninediabetes.org/cdinsulin.html. Accessed January 12, 2011.
  6. Palm CA, Boston RC, Refsal KR, et al. An investigation of the action of neutral protamine hagedron human analogue insulin in dogs with naturally occurring diabetes mellitus. J Vet Med. 2009;23:50-55.