Insulin: Protamine Zinc

What is protamine zinc insulin?

Protamine zinc (PZI) insulin (brand name ProZinc®) is an injectable medication approved for use in cats and dogs with diabetes mellitus. It is used to lower blood sugar levels and for long-term maintenance therapy of diabetes mellitus.

This medication may be used “off label” or “extra label” in other species. Many drugs are commonly prescribed for off-label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully.

How do I give my pet protamine zinc insulin?

Protamine zinc insulin comes in injectable form in vials. 

• Injections are given subcutaneously (under the skin). 
• Use only U40 syringes with protamine zinc insulin.
• This medication should be given at the same time every day.
• This medication should be given after a meal. If your pet is not eating, do not give this medication and consult your veterinarian for further instructions.
• Follow injection instructions provided by your veterinary team. Ensure the correct dose is drawn and given each time. 
• Contact your veterinarian if you have difficulty drawing up the medication or giving injections.
• Give this medication to your pet for the entire time prescribed by your veterinarian; do not stop giving this medication suddenly.

What if I miss giving my pet the medication?

A single missed dose can cause temporary signs, but it is usually not life-threatening. Contact your veterinarian as soon as possible for advice on when to give your animal’s next dose. Never double-up on doses as this will cause an overdose. If your veterinarian cannot be reached, and your animal is eating and acting normally, give your animal the usual dose at the next regularly scheduled time.

Are there any potential side effects from protamine zinc insulin?

Protamine zinc insulin may cause the following side effects:

• Lumps or thickening of skin at the injection site
• Signs of high blood sugar (e.g., excessive thirst, frequent urination, increased appetite)

The following reactions are rare, but if they occur, contact your veterinarian immediately:

• Sgns of low blood sugar such as weakness, lack of energy, lethargy, stumbling or difficulty walking, behavior changes, muscle twitching, seizures (convulsions), and/or unresponsiveness.
• An allergic reaction such as irregular breathing, rash, fever, puffiness and swelling around the face

Drug sensitivities can develop over time with repeated exposure. Your pet may have no reaction after the first few doses but may develop a sensitivity later. It is important to watch for signs of an allergic reaction over the entire course of treatment.

Other side effects may occur. If you notice anything unusual, contact your veterinarian immediately. This long-acting insulin lasts for 7–18 hours in cats and 6–28 hours in dogs.

Are there any risk factors for this medication?

This medication should be AVOIDED in animals who:

• Are allergic to any component
• Are not eating
• Show signs of low blood sugar or have confirmed low blood sugar (hypoglycemia)

If you suspect your pet’s blood sugar level is low, contact your veterinarian immediately. Hypoglycemia is a potentially fatal emergency.

Are there any drug interactions I should be aware of?

Certain medications should be USED WITH CAUTION when given with protamine zinc insulin, including: 

• Medications used to treat heart conditions and/or control blood pressure (e.g., aspirin, beta-blockers, angiotensin-converting enzyme inhibitors [ACEIs], calcium channel blockers, angiotensin II receptor blockers [ARBs], digoxin, diuretics, reserpine, disopyramide)
• Oral glycemic control medications (e.g., glipizide)
• Albuterol, terbutaline
• Clonidine
• Fluoxetine, MAOIs (monoamine oxidase inhibitors)
• Certain types of antibiotics (sulfonamides, fluoroquinolones)
• Estrogens, progestins
• Thyroid hormones
• Certain medications used for sedation (e.g., acepromazine, dexmedetomidine, xylazine)

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking before starting any new treatment.

Is there any monitoring that needs to be done with this medication?

• When starting protamine zinc insulin, your veterinarian will monitor baseline blood work and urinalysis to check organ function and for urinary tract infections.
• Close monitoring of blood sugar levels and overall health is required (e.g., appetite, energy, thirst, weight). Consult with your veterinarian for specific recommended monitoring for your pet.

How do I store protamine zinc insulin?

• Refrigerate unopened vials and pens. Do not freeze.
• Veterinarian internal medicine specialists indicate protamine zinc insulin may be used for 3–6 months after opening if stored properly, whereas manufacturing labels may recommend discarding 60–80 days after opening. Follow your veterinarian’s recommendations on when to discard the medication.
• Discard medication if cloudy or discolored.
• Follow your veterinarian’s recommendations on disposal of used sharps.
• Keep medication out of reach of children and pets.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.