Chronic renal failure is a major problem in older cats and dogs. Unfortunately, very few treatments change the progression of the disease, so it becomes especially important to control the few things that can prolong survival. Among these interventions would be monitoring for urinary tract infection, monitoring for hypertension, and controlling parathyroid hormone levels. 

Calcitriol is the key to controlling hyperparathyroidism. When it's used early in renal failure, the dose that will be effective is predictable and less expensive monitoring is necessary. This is the best use of the drug -- to start it before the parathyroid hormone levels increase. However, it's never too late in the progression of renal failure to start it -- but starting later means the dose of calcitriol is less predictable, so more monitoring of parathyroid hormone levels is required. In addition, starting later usually means that we have to work first to make the phosphorus level drop below 6.0 mg/dl -- calcitriol physically can't work when the phosphorus level is higher. To do this requires a combination of a low protein (also low in phosphorus) diet, and frequently the use of aluminum hydroxide (trade names Amphogel, Alternagel, Basaljel) to bind phosphorus in the diet. Once the phosphorus level drops, then usually the phosphate binder isn't required for the long run.

Not only is calcitriol working silently to prolong survival, but it actually causes the animal to feel better--better appetite and more activity. 

In the veterinary literature, some confusion has been caused by the publication of opinions by a particular group of nephrologists who feel strongly that calcitriol is dangerous in renal failure animals. This opinion is based on their interpretation of studies they performed using calcitriol--they used high doses of calcitriol, and repeatedly caused the animals to have high serum calcium levels. Indeed, if you use calcitriol at those doses, that is a major risk, and hypercalcemia is detrimental to kidney function. However, those doses of calcitriol are not being used to control renal secondary hyperparathyroidism -- we can control parathyroid hormone effectively with doses ranging from 1/3-1/4 of those high doses, thus making the drug very safe. Some monitoring is required of calcium and phosphorus levels, but renal damage is not seen ... in fact the opposite is true ... renal function is spared.

I remember when calcitriol was just a new thing some people at OSU were studying. One of my internmates was in charge of the University Emergency Service and had a renal kitty and was very interested in calcitriol information and passed it on to me.  When I first added calcitriol to my standard therapy for renal kitties I could not believe the results. The survival time increased. For the first time I got kitties who actually could go off SQ fluids after having been on them for months. I see a big prognostic difference in the kitties who are candidates for calcitriol (phosphorus level still normal) and those who are not candidates (phosphorus too high). When we get a cat to cross groups with fluid therapy, diet or whatever, we see the same good results as with the cats who had been on calcitriol from the beginning. I know this is subjective  (after all, I am just treating cats in practice, not conducting a research study) but I think the advent of Calcitriol has been one of the biggest breakthroughs in the management of renal disease in the cat.

I have treated quite a few cats and have been pleased with what I have seen.  The problem with calcitriol is there haven't been good controlled studies to this point and many are reluctant to use it because of this.  Additionally, there has been some work to suggest its utility in the treatment of CRF cats but some of the data was misinterpreted by some.  I will continue to use it whenever I have a CRF cat presented to me. 

In September 1993 I was presented with my first patient that was being treated with calcitriol. This adorable elderly cat named Deluxe had been diagnosed with CRF three years earlier and had entered into a study using calcitriol with Dr. Nagode at Ohio State University. At the time I was very impressed with at Deluxe’s longevity and vigor. At that time I had never seen a cat with that level of kidney failure live so long and with good quality ! of life. Before using calcitriol I would have expected Deluxe to live 9 to 18 months after diagnosis. Deluxe lived an additional nine months and died of an unrelated disease condition, thus Deluxe lived almost twice as long I could have hoped for. 

I am thrilled to have a calcitriol to offer clients with CRF pets. Calcitriol is an easily administered, effective medication that has the potential to substantially increase longevity and quality of life especially when used early in the course of disease. In our practice every client with a pet diagnosed with CRF is introduced to the idea of using calcitriol. While it is not the right choice for every client and pet it is a very useful and beneficial medication for many pets with chronic kidney failure. When my own sixteen-year-old dog, love of my life, developed kidney failure she started on the preventive low dose calcitriol protocol.

Sandra Coon, DVM
Broadway Veterinary Hospital and Laser Surgery Center
1824 12th Ave
Seattle, WA 98122
http://www.broadwayvh.com

I will summarize my experience with calcitriol.  Since December of 1994 I have filled 643 feline prescriptions and 80 canine prescriptions for calcitriol. These prescriptions have mostly been for 60 day treatment lengths for cats and 100 day treatment lengths for dogs.  Calcitriol in all these cases was prescribed for CRF cases in which the phosphorus was below 6.0. The dose for calcitriol was 2.5 mg/kg.  Calcitriol was stopped when the serum phosphorus levels rose above 6.0, when hypercalcemia developed, when it was not tolerated by the pet (rare), or the owner was unable to give (rare, also).

After reviewing Drs. Nagoda and Chew’s protocol for calcitriol use on your website I must admit that my patient monitoring of PTH levels and adjusting of calcitriol doses has been very limited.

Having said this, I believe calcitriol is an important addition to early CRF treatments. I always try dietary therapy but as we all know this is hit or miss, especially with cats.  The control of hypertension and oral potassium supplements when appropriate are very important therapies as well.  I would estimate that at least 25% of the CRF cats that I see are not hypertensive and won’t eat a therapeutic diet or any food with potassium added (or the owners are unwilling to pill).  In this subpopulation of cats calcitriol may be your only hope of slowing down the progression of CRF (short of fluid therapy).  Clinically, I have seen many cats improve on calcitriol only.  Weight gain and improved appetites and activity levels are the most common changes noted.  Creatinine and BUN levels often stabilize and sometimes improve.  In general practice I believe the two most underused CRF therapies are the use of calcitriol and the control of hypertension.

Joe Whalen, DVM (11/30/2002)

One of the most influential drugs to be used by our practice in the treatment of kidney disease is Calcitriol.  Calcitriol is a vitamin D analog.  Its role in the treatment of kidney disease is very complicated but its overall effect is to decrease the levels of a specific hormone (parathyroid hormone) that can be detrimental to the patient who is experiencing kidney problems.  We have had excellent results with this drug.  In fact, it is the single most important new treatment that we can offer our patients.  This drug greatly improved the prognosis for our patients who have early kidney disease and has been very important in extending many of our patient’s lives.  Calcitriol is administered once daily orally and is well tolerated by our patients.  Even cat owners seem to be able to medicate their feline friends with minimal fuss.