Veterinary : Endocrinology
- Diabetes, Thyroid, and Adrenal Disease
PZI and Low-Dose Insulin
The commercial production of traditional beef &/or pork insulins
has declined as most human diabetic patients (the majority of the
consumers) are being switched to human insulin products because of
the reduced risk of allergic reactions. Protamine zinc insulin occurs
as a sterile suspension of insulin modified by the addition of protamine
sulfate and zinc chloride, and has a long duration of action (up
to 30 hours). Therefore, treatment of many dogs and cats has been
accomplished with once daily dosing of PZI.
U-20 and U-40 insulin allow for more accurate measurement of smaller doses required
by many pets and birds. Use of U-100 insulin can result in morbidity or mortality
caused by dosing errors.
Please call our compounding pharmacy for more information about these insulin
preparations for animals.
Oral Anti-Diabetic Drugs
“may be appropriate for cats that are in good overall health with early
or mild clinical signs of diabetes and those with owners who are unwilling or
unable to administer insulin injections.”1 The oral hypoglycemic medication,
glipizide, provides a viable therapeutic alternative to conventional insulin
therapy with a positive therapeutic response in approximately 50% of diabetic
cats with non-insulin-dependent disease. Response to glipizide therapy or lack
thereof usually is evident within the first 4 to 6 weeks of treatment. Adverse
side effects occurred in less than 10% of patients. The existence of residual
beta cell function is necessary for response to glipizide therapy. Discontinuation
of diabetogenic medications that may be contributing to insulin resistance is
According to Deborah S. Greco, DVM, Ph.D., diplomate ACVIM, glipizide has been
used successfully to treat diabetes mellitus in cats at a dosage of 2.5 to
5 mg two times daily, when combined with dietary fiber therapy. Dr. Greco recommends
evaluating the patient weekly or every two weeks for a period of 2 to 3 months.
If the fasting blood sugar decreases to less than 200 mg/dL, the glipizide
should be continued at the same dosage and the cat reevaluated in 3 to 6 months.
If the fasting blood glucose remains >200 mg/dL after 2 to 3 months of therapy
and the cat is still symptomatic (polyuria, polydipsia, weight loss), glipizide
should be discontinued and insulin therapy instituted. If the blood glucose
remains >200 mg/dL and the cat becomes asymptomatic, glipizide should be
continued indefinitely and the cat rechecked in 3-6 months.3
1 Compendium 23(7), July 2001, 633-640
2 Vet Clin North Am Small Anim Pract 1995 May;25(3):599-615
here to access the PubMed abstract of this article.
3 presented at the 1999
Southern California VMA Seminar and the 116th Indiana VMA Seminar
Methimazole for Feline Hyperthyroid Disease
“Methimazole is the drug of choice for the medical management of feline
hyperthyroid disease. It is safer and more potent than propylthiouracil in blocking
thyroid hormone synthesis. Use of the drug generally will bring serum T4 into
normal ranges within 2 to 3 weeks... Adverse effects have been observed in approximately
15% of cats and generally are transient. Anorexia, vomiting, and transient lethargy
have been reported. Serum antinuclear antibodies develop in many cats with long-term
use of the drug. A glucocorticoid-responsive pruritus involving the face, ears,
and neck may occur. In less than 2% of cases, thrombocytopenia or agranulocytosis
have been reported in cats treated with [methimazole]. Withdrawal of the drug
and provision of care for thrombocytopenia or agranulocytosis generally results
in resolution... Cats on chronic methimazole therapy should be rechecked every
3 to 6 months to assay serum T4 levels and to check for signs of drug toxicity.”
Handbook of Veterinary Drugs, 2nd edition, ©1998, pp. 239-240
According to the International Journal of Pharmaceutical Compounding (Vol.
5, No. 2, March/April 2001, p. 96), “it could be theorized that transdermal
administration would produce a ... higher blood level of methimazole than that
resulting from oral administration of the drug. A higher blood level of [methimazole]
might result in a slightly greater risk of adverse effects, so drug therapy
might need to be initiated at a slightly lower dose than that of the traditional
oral dose.” The author of the article (GiGi Davidson, R.Ph., DICVP, North
Carolina State University, College of Veterinary Medicine) states that anecdotal
evidence indicates that this is true of “most transdermally administered
doses of methimazole. The most measurable parameter for efficacy is the response
of the serum T4 level.”
Note: Methimazole is also used to decrease renal toxicity of cisplatin in
Transdermal Methimazole Applied to Ear of Hyperthyroid Cats
Francis Arsenault, D.V.M., New Brunswick
The following six cats have received methimazole in a pluronic
lecithin organogel (PLO) which the owners apply to the inner side of the ear.
Overall, we have found this to be very effective therapy with good compliance.
Transdermal administration can be particularly helpful for owners who have
arthritis and those who have great difficulty “pilling” the cat. Methimazole doses have ranged
from 2.5mg to 12.5 mg daily, divided into two doses.
Cat #1 (S.A.): 17 years old, has been on methimazole 1.25mg/0.1 ml PLO to
inside of ear twice daily for nine months. The owner reports that the medicine
is easy to administer and absorbs well. I am pleased with the clinical results.
Cat #2 (A.L.): 18 years old, has been using methimazole for six months. This
cat was started on 3.5mg/0.1ml PLO BID. Several dosage adjustments were necessary.
We increased the concentration of the transdermal gel to 5.0mg/0.1ml PLO,
and the owner now applies 7.5mg/0.15ml PLO in the AM and 5mg/0.1ml in the
PM. She places plastic wrap over her finger before applying the medication,
which she has found to be much easier to use than pills, with no stress to
the pet. She states the measurements on the topical dispenser are easy to
read, and she needs to wash the cat’s ear to remove the coating left by the medication.
Cat #3 (B.M.): was started on methimazole eight months ago at 5mg/0.1ml PLO
BID. The dose was decreased to 2.5mg BID. The cat’s owner stated the
medication was very easy to use. B.M. improved clinically and gained weight,
and is no longer on the med.
Cat #4 (S.O.): used medication once only.
Cat #5 (D.O.): same owner as cat #4, received methimazole 2.5mg/0.05ml PLO
BID for two months. No longer on medication.
Cat #6 (M.B.): 19 years old, has received methimazole 1.25mg/0.1ml PLO BID
for four months. The owner says the medication is easy to apply, and alternates
ears. It is necessary to wipe the ear each day as the medication does leave
Adrenal Disease in Male Ferrets
Adrenal gland disease is a common problem in middle-aged to older ferrets.
The disease results in one or both of the adrenal glands producing abnormal
amounts of androgens and/or estrogens, and can cause hair loss, itching,
vulvar enlargement in females, prostate enlargement in male ferrets which
can block the flow of urine, and in rare cases, bone marrow suppression.
Although not usually a serious health concern, ferrets may have no relief
from the itching that is associated with this disease if it is not treated.
Flutamide is an androgen blocker that may help relieve prostatic enlargement.
It is dosed at 10 mg/kg, PO, every 12-24 hours. Liver enzymes should be checked
at one month and every six months thereafter. Mitotane may be effective in
younger ferrets but may cause nausea and lethargy. Ketoconazole is usually
1 Evelyn Ivey, DVM, Dip ABVP, San Diego Co VMA Conf Procd, Sep 2000
Mitotane for Canine Hyperadrenocorticism
In veterinary medicine, mitotane is used primarily for the medical treatment
of pituitary-dependent hyper-adrenocorticism (PDH) and palliative therapy
of adrenal carcinoma, usually in dogs. Systemic drug availability has been
found to be very poor from intact tablets in fasted dogs, and best when the
powdered drug is mixed in oil and poured on dog food. The interaction between
food and mitotane probably contributes to the variation in clinical response
of dogs treated with the drug, because it appears that the efficacy is improved
considerably when the drug is given with food. Because of the potentially
severe toxicity associated with mitotane, clients should be instructed to
wear gloves during and wash their hands after administering the medication,
and to keep the medication out of reach of children or pets. Dogs with concurrent
diabetes mellitus may have rapidly changing insulin requirements during the
initial treatment period, and should be closely monitored until they are
clinically stable. Clients should be advised of the symptoms of acute hypoadrenocorticism.
Because of the potential severe toxicity associated with mitotane, clients
should be instructed to wash their hands after administration and to keep
the medication out of reach of children or pets.
Res Vet Sci 1987 Sep;43(2):160-5
Veterinary Drug Handbook, 2nd Edition, by Donald C. Plumb