Renal Treatment in Aging Pets



Geriatric Pets
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 cats.

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.

References:

"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