Veterinary Prescription Resources

As more consumers look to have their veterinary prescriptions filled by a community or mail order pharmacy, pharmacists are playing an increasing - and important - complementary role in the health care of animal patients. Given this emerging role, it is important that pharmacists contact veterinarians directly with any concerns about the patient’s prescription.

It also is good to keep the following in mind when filling and dispensing prescriptions:

Diabetes mellitus (DM) is a common disease encountered in canine and feline medicine.  As in human medicine, treatment of diabetes mellitus can be challenging, as it requires attention and committed efforts from both the owner and the veterinarian to adhere to a consistent protocol for glycemic control.  Community pharmacists must note, however, that there are major differences between diabetes in cats and dogs versus diabetes in humans, specifically in regards to treatment options.  Even the slightest variation from a treatment plan can affect the health of the cat or dog, leading to poor glycemic control, which, if left unattended, may lead to life-threatening diabetic ketoacidosis and hypoglycemia. 

Feline DM:  

Type 1 DM is rare in cats and most cats with diabetes have type 2 DM (80%), which is caused by insulin resistance and relative insulin deficiency secondary to β cell dysfunction.  Additionally, it is not unusual for cats to go into spontaneous clinical remission within 1-4 months after treatment is initiated, especially if clinical intervention is managed early, aggressively and effectively.  Predisposing risk factors for feline DM include: physical inactivity, obesity, older than 8 years of age, high-carbohydrate diet, gender (male neutered), certain breeds, drug therapy (i.e. corticosteroids), and concurrent conditions (i.e. infection, hyperthyroidism, and chronic renal insufficiency).  Clinical signs of feline DM may include: polyuria, polydipsia, polyphagia, obesity with recent weight loss, lethargy, dehydration, poor hair coat, hepatomegaly, and neuropathy representative of difficulty jumping, hind limb weakness, and plantigrade posture. 

Canine DM:

The majority of dogs that have diabetes mellitus are insulin-dependent or Type 1 and are likely to remain diabetic for life due to a relative or absolute lack of insulin secretion secondary to β cell dysfunction/absence which is irreversible.  Predisposing risk factors of canine DM include: breed, middle-aged/older females, and concurrent conditions (i.e. infection, drug therapy, obesity, immune-mediated destruction, and pancreatitis).  Clinical signs of canine DM include:  polydipsia, polyuria, polyphagia, weight loss, dehydration, electrolyte imbalances, metabolic acidosis, frequent urinary tract infections, osmotic diuresis, lameness (due to peripheral neuropathy), or vision loss from cataracts.  

Therapy Goals and Assessment:

The therapy goals and assessment for each animal patient is individualized, and treatment may be modified based on response.  Blood glucose levels should be maintained between 120 mg/dL to 250 mg/dL in cats and between 100 mg/dL to 250 mg/dL in dogs.  Blood glucose control is not as strict as in humans due to the risk of hypoglycemia.  While the administration of insulin is the foundation of medical therapy management, other factors are also important for managing DM in canine and feline patients.  These factors include clinical remission if possible (cat), minimizing clinical signs (i.e. polyuria/polydipsia), dietary selection, weight control, treatment of concurrent illness, avoiding complications such as ketoacidosis and hypoglycemia [blood glucose <60mg/dL (cat) and <80mg/dL (dog)], avoiding sequelae (i.e. neuropathy or cataracts), and frequent reassessment by the veterinarian.  

Choice of Insulin Treatment:

Veterinarians use a variety of veterinary and human insulin products.  Only Vetsulin® and ProZinc® are approved by the FDA for use in dogs and cats.  All other insulins are used extra-label.  It should be noted that veterinary insulins have a concentration of 40 units/mL and require U-40 syringes for dosing to avoid the risk for major dosing errors.  Oral hypoglycemics (i.e. glipizide) are not effective in dogs due to the absence of functional β cells.  Glipizide may be used in cats when owners are unable or unwilling to administer insulin.  However, it has been associated with the destruction of β cells and may become ineffective over time.

• Vetsulin® 40 units/mL (porcine insulin zinc suspension; Merck Animal Health) 
• Intermediate-acting insulin most commonly used in dogs
• Initial dose in dogs is 0.25 units/kg subcutaneously every 12 hours after meals
• Duration of action is between 10 to 14 hours in dogs
• Usual dosage (euglycemia maintenance) in cats is 1 to 2 units subcutaneously every 12 hours with or immediately following a meal (this insulin is usually reserved for cats unresponsive to other types of insulin due to its short duration of action)
• Must be shaken well before use to form homogeneous suspension 
• Injections must be administered using U-40 syringes only 
• Available in 10 mL vial or 2.7 mL pen cartridges (used with VetPen insulin pen)
• Store in the refrigerator and use within 42 days of first puncture

• Insulin glargine 100 units/mL (human recombinant; Lantus®; Sanofi) 
• Long-acting insulin commonly used in cats due to its duration of action
• Usual dosage (euglycemia maintenance) in cats is 1 unit subcutaneously every 12 hours with or immediately following a meal
• Although glargine can be used in dogs it is not recommended for initial treatment of newly diagnosed diabetic patients due to unpredictable efficacy
• Available in 10 mL vial or 3 mL prefilled syringe cartridge 
• Store in refrigerator and use within 28 days of first puncture
• Do not shake, dilute, or mix with other insulins

This article is not an all-inclusive practice management topic on diabetes management for dogs and cats but a brief overview of pharmacy practice highlights for the community pharmacists’ understanding.  For further information, practicing pharmacists and pharmacy technicians are encouraged to obtain continuing education via Power-Pak C.E.® ‘Veterinary Pharmacy Certificate’ program and to build a library of veterinary references and texts.

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