| 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 important.2
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
Click 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 dogs.
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 a residue.
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 ineffective.1
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 |
