Chronic renal failure, common in elderly humans is now common - and
treatable - in pets.
If you think back a few decades you remember how uncommon it was to hear of
dogs older than ten years. Now it is not at all unusual to hear of dogs over
15 years old, and cats over 20 years old! The advances in veterinary
medicine and nutrition can take credit for these remarkable advances. What
if human medicine discovered comparable longevity secrets? In the space of a
generation average lifespans would increase by 50%!
The downside to increased life expectancy for pets is that they now commonly
exhibit the same symptoms associated with old age in people. One of these is
the reduction in kidney function, and since this is a progressive condition
it ultimately leads to renal failure.
As kidney function declines, blood phosphorous levels increase and the
kidneys produce less of a chemical called calcitriol, which is the
biologically active form of Vitamin D. Replacement of calcitriol is a
logical treatment in this case. Calcitriol (1,25 dihydroxycholecalciferol,
human-use drug, brand name: Rocaltrol) is prescribed for humans to reduce
elevated parathyroid hormone levels (PTH), which are the result of
diminished kidney function and calcitriol deficiency.
Human prescriptions are typically for doses of 0.250mcg or 0.500mcg of
calcitriol (Rocaltrol), taken orally once daily. Normally, you would assume
that a proportionately smaller dose would be appropriate for a pet.
Unfortunately, this is not the case and attempts to use calcitriol at an
approximate fraction of the human dose result in hypercalcemia, or a level
of calcium that is too high. Because of this calcitriol treatment for
animals experiencing renal failure was not recommended - until recently.
Based on further studies at Ohio State University, School of Veterinary
Medicine, it was found that dogs and cats actually need much lower doses of
calcitriol. These studies, conducted by Dr. Larry Nagode, DVM, MS, Ph.D. and
Dr. Dennis Chew, DVM, ACVIM of the Dept. of Veterinary Biosciences,
determined the appropriate dosage levels and have made it possible to treat
chronic renal failure, one of the most common ailments of older dogs and
The result of extensive clinical trials by Dr. Nagode and Dr. Chew was an
optimal dosing range of 1.5ng/kg to 3.5ng/kg, orally once daily for the
treatment of renal secondary hyperparathyroidism. Follow-up blood tests that
measure serum calcium, phosphorous and PTH levels determine the dose within
this range for each animal. If the dose is too low the calcitriol levels
will remain below normal. If the dose is too high calcium levels will exceed
safe levels. Ultimately, the dose prescribed and the benefits anticipated
depend on the stage of kidney failure at which calcitriol therapy is begun.
The benefits of calcitriol treatment were measured in a subsequent survey
involving over 500 dogs and 1000 cats. This survey resulted in 80% of dog
owners and 85% of cat owners responding that their pets seemed brighter and
more alert and interactive after beginning calcitriol therapy. The reason
for this marked improvement is presumed to be the reversal of the effects of
central nervous system depression usually resulting from elevated PTH.
Secondly, the survey results found 77% of dog owners and 84% of cat owners
reporting an improvement in appetite. This finding is significant because
weight loss and inappetance are two symptoms that often lead to the initial
diagnosis of chronic renal failure.
Third, the survey reported that 77% of dog owners and 79% of cat owners felt
their animals were more physically active than previously. Research has
shown that calcitriol therapy lowers PTH, which has a toxic effect on
peripheral nerves, the skeletal muscles, the heart, and the bones.
Finally, and most importantly, the survey asked the prescribing
veterinarians for their opinions on the benefits of calcitriol therapy. In
88% of the cases with cats, and 83% of the cases with dogs the doctors
agreed that, compared to patients in comparable stages of renal failure, the
calcitriol treated patients seemed to have longer lifespans.
These results have been confirmed in hundreds of conversations with pet
owners contacting Island Pharmacy Services. Numerous pets have now been
receiving calcitriol prescriptions for years after they were diagnosed with
chronic renal failure. As the studies have scientifically confirmed, daily
oral calcitriol at low doses is both safe and effective in the control of
renal secondary hyperparathyroidism in dogs and cats. Low doses of
calcitriol are most effective when started early in uremia before the onset
of advanced stages of renal hyperparathyroidism.
Island Pharmacy Services has filled hundreds of prescriptions for calcitriol
over the past years. The difficulty in pet owners obtaining this drug
locally is due to the minute doses prescribed. For example, a typical adult
cat would require a daily dose of 8ng (nanogram.) A nanogram is 1/1000 of a
microgram, or 1/1,000,000 of a milligram! Rocaltrol, the human-use brand
name drug is manufactured in 250ng or 500ng liquid-filled gel capsules, not
hard tablets that could be approximately divided.
Island Pharmacy Services has perfected the compounding of the minute doses
of calcitriol required for dogs and cats. We have invested in laboratory
instruments capable of accurately dispensing doses as small as 4ng. We
currently prepare calcitriol doses in both capsules and oral solutions.
Questions regarding calcitriol-compounded doses are always welcome. Please
call IPS toll-free at 800-328-7060.
"Benefits of Calcitriol Therapy and Serum Phosphorous Control in Dogs and
Cats With Chronic Renal Failure", Vet. Clinics of N. America: Small Animal
Practice, Vol. 26, Number 6, Nov. 1996: 1293-1330
"The Use of Low Doses of Calcitriol in the Treatment of Renal Secondary
Hyperparathyroidism", In 15th Waltham Symposium (Endocrinology), 1992: 49-63
"Nephrocalcinosis Caused By Hyperparathyroidism in Progression of Renal
Failure: Treatment with Calcitriol", Seminars in Vet Medicine and Surgery
(Small Animal), Vol. 7, No 3, (August) 1992: 202-220