A panel of veterinary specialists and general practitioners discuss their real-world experiences in providing successful care to diabetic cats.
FELINE DIABETES is one of the most common and challenging diseases you'll encounter in small-animal practice. Treatment can be confusing because each patient is unique and management options continue to evolve. Whether faced with a newly diagnosed diabetic cat or an unregulated long-term patient, the entire veterinary team and the client must work together for successful management. To assist in your treatment recommendations, a panel of veterinary specialists and general practitioners recently convened to discuss their real-world experiences in providing successful care to diabetic cats. All the participants have a strong interest in feline diabetes prevention and management and have extensive experience in treating diabetic cats.
Dr. Sara L. Ford (moderator): The first question we'll tackle is the prevalence of feline diabetes in our practices. We'll start with Dr. Edlin since he is in general practice with a more representative sampling.
Moderator Sara L. Ford, DVM, DACVIM VCA Emergency Animal Hospital San Diego, Calif.
Dr. Gary Edlin: We have about 1,700 feline patients; of these, we treat about 100 diabetic cats.
Gary Edlin, DVM East Louisville Animal Hospital Louisville, Ky.
Dr. Gary D. Norsworthy: I have about 15,000 to 18,000 feline patients in my practice. We diagnose a new case of feline diabetes about three times a month, and we typically have at least 50 active diabetes cases at any one time. A few of these are referrals, but the vast majority are my primary care patients.
Gary D. Norsworthy, DVM, DABVP Alamo Feline Health Center San Antonio, Texas
Dr. Ford: Would one of the specialists please comment?
Dr. Claudia A. Kirk: We probably see about 50 cases of diabetes per 2,000 cats admitted. These cats have already been diagnosed with diabetes in our practice. I think the prevalence depends on the feline patient population you are evaluating. It is going to be about two or three in 100 cats in a referral practice where we are skewed toward seeing challenging diabetic cases. One reason for the increasing prevalence in recent years is the larger population of neutered cats—a risk factor for both obesity and diabetes.
Claudia A. Kirk, DVM, PhD Department of Small Animal Clinical Sciences College of Veterinary Medicine The University of Tennessee Knoxville, Tenn.
Dr. Mark E. Peterson: My sense is that diabetes is becoming more common, probably because cats keep getting fatter. Since all the cats I see are referred for problem diabetes, I can't comment on prevalence, but I see a new diabetic cat every week or two.
Mark E. Peterson, DVM, DACVIM Animal Medical Center New York, N.Y.
Dr. J. Catharine Scott-Moncrieff: It is also a geriatric disease, so as cats live longer the prevalence increases.
J. Catharine Scott-Moncrieff, Vet MB, MS, MA, DACVIM, DECVIM Department of Veterinary Clinical Sciences School of Veterinary Medicine Purdue University West Lafayette, Ind.
Dr. Ford: The diagnosis of feline diabetes rests on finding persistent hyperglycemia and glucosuria. Clinical signs of diabetes are subtle to most owners, especially in the initial stages. So, what is the prognosis for a feline diabetic patient?
Dr. Peterson: If a diabetic cat has acromegaly or another complicating disease, the long-term prognosis is poor. However, if it doesn't have any concurrent diseases, the prognosis can be very good.
Dr. Scott-Moncrieff: The prognosis totally depends on the owner's commitment and whether the animal has concurrent illness associated with diabetes. I've seen patients that have been diabetic for five, seven, or even 10 years. Having a committed owner is the key.
Dr. Norsworthy: How rigid the veterinarian is with treatment recommendations is critical to client cooperation. I've had clients tell me, "My husband and I have not gone out to dinner together since our cat was diagnosed with diabetes because the cat needs insulin at dinnertime." I did not mean to be that rigid when I discussed treatment. Some people take everything you say literally, such as treating their cats every 12 hours. On the other hand, I remember telling a client that his cat would need a special diet, insulin injections twice a day, and monitoring. The man said he could not treat his cat. Such clients are unwilling to change their lifestyles at all for their cats, so the cats have a very poor prognosis. Clients like these often choose euthanasia rather than treatment.
Dr. Scott-Moncrieff: Sometimes it can be helpful to have owners with newly diagnosed diabetic cats talk to someone who has had a diabetic pet. I had a diabetic dog of my own for three years, and I think that helped me relate to owners about what kind of flexibility they can build into their schedules.
Dr. Richard W. Nelson: My experience is a little different. I have had to euthanize diabetic cats because of progressive neuropathies. Prognosis is tied to regulating their diabetes. In our referral practice, I'll bet 25% of the diabetic cats have neuropathy. Owner commitment, the nature of the concurrent disease, and complications related to the ability to establish reasonable control are the most important factors determining outcome.
Richard W. Nelson, DVM, DACVIM Department of Medicine and Epidemiology School of Veterinary Medicine University of California, Davis Davis, Calif.
Dr. Norsworthy: The American Veterinary Medical Association published a study a few years ago where they looked at several factors that determine whether an owner will treat a chronic disease.1 The most important factor was the way the veterinarian presented the treatment and prognosis information. How the management plan is presented greatly impacts the quality of treatment for the diabetic cat. I say, "Boy this is great. With the proper treatment, your cat is going to live a very long time and will probably die of something other than diabetes."
Dr. Ford: Let's switch gears now and talk about treatment. Which insulin therapies do we recommend for our feline patients?
Dr. Norsworthy: Protamine zinc insulin (PZI) has always been my preference going back to my early practice years in the 1970s. Now that ProZinc® (Boehringer Ingelheim Vetmedica, Inc.), which is protamine zinc recombinant human insulin, is available, it is my insulin of choice. There are a lot of variables when treating diabetic cats, so I use a product that works consistently. I have never prescribed Lente insulin for a cat. I have examined a couple of cats that were being treated with it; they were not well-regulated, so I switched them to PZI or ProZinc. I've had a few cats come to me that were treated with glargine insulin, and if they weren't doing well I'd generally change to PZI. It's been my drug of choice forever.
Dr. Edlin: I also like ProZinc for its predictable duration of action and, therefore, ease of regulation.
Dr. Peterson: Most of the diabetic cats I see are already on insulin therapy (usually NPH or Lente) and are referred to me because of difficulties in regulation. As a first step in the investigation of a cat's problem diabetes, I routinely switch these problem diabetics to ProZinc administered twice daily. In those few cats that do not respond adequately to ProZinc, I'd then try either glargine or detemir insulin.
Dr. Kirk: We keep diabetic cats on their current insulin and try to regulate them. Then if regulation is challenging, we typically use either glargine or ProZinc. These cats often are being treated with another human recombinant insulin or Lente insulin. We try not to change insulin products unless it really seems to be part of the problem. We go through the standard routine, including investigating how owners are giving the insulin and what they are feeding. We look at the entire administration and home care process before we change the insulin.
Dr. Nelson: The biggest issue we have with diabetic cats is that the insulin has a short duration of effect. That's been the problem as a general rule. We often used PZI in the 1980s. But PZI wasn't working well for me, and I had switched to Lente and Ultralente insulin at the time PZI was taken off the market. When I was asked to be involved in the FDA PZI efficacy trial in the late 1990s,2 I was skeptical. However, most of the cats we treated with PZI did really well. I became a believer in PZI again. Now I like it because its duration of effect is in the middle and it allows me to switch to a shorter- or longer-duration insulin if necessary. If I have difficulty with too long of a duration with PZI, I switch to Lente insulin (Vetsulin® [porcine zinc insulin]—Intervet Schering-Plough). If PZI has too short of a duration, I switch to glargine. I also believe in supporting veterinary products in which the company has gone through the strenuous ordeal of obtaining FDA approval. If we lose the two FDA-approved insulins for use in cats and dogs, we are in real trouble, as illustrated by the current limited availability of Vetsulin.
Dr. Edlin: I had eight diabetic cats in the ProZinc safety study at its completion.3 They did very well. ProZinc was provided to the owners after the study. Two of the owners were from other practices, and their cats were placed back on glargine or Ultralente when the ProZinc supply ran out. Both owners contacted me saying that the cats had become unregulated and they wanted more ProZinc.
Dr. Norsworthy: I was involved in the first PZI study where cats that were regulated on the old PZI product were switched to the new PZI product, ProZinc, for 30 days and monitored.4 It was a relatively short period of time, but at the end of that study three out of the 10 owners that I dealt with said their cats were doing much better on the ProZinc and they wanted more.
Dr. Ford: If you have an uncomplicated diabetic, what PZI dose would you start with?
Dr. Norsworthy: I would start with 0.25 units/lb, which typically is about two units twice a day. That is a very conservative dose. I always live by the rule that it is better to underdose than overdose. So I start low and use that dosage for a week and then recheck and adjust it accordingly.
Dr. Edlin: I use the same initial dose of PZI: 0.25 units/lb.
Dr. Scott-Moncrieff: I am more conservative with the dose. I don't see that many newly diagnosed diabetics, but I usually start them out at one unit twice a day. I do this because I've had some really big cats become hypoglycemic if they're started at higher doses. I typically start out using PZI insulin for the reasons already discussed.
Dr. Ford: What about once-a-day dosing and long-acting insulin?
Dr. Nelson: I've never had luck with once-daily insulin regardless of the preparation. Besides needing to dose twice daily, the issue that I see with glargine is the belief that glargine is a peakless insulin in diabetic cats. In some diabetic cats, administration of glargine results in a prolonged mild increase in blood insulin concentrations that leads to minimal fluctuation in the blood glucose concentration. However, in some cats glargine behaves just like other insulins: it produces a marked increase in insulin that causes the typical U-shaped glucose curve with a defined peak in blood insulin and a defined glucose nadir. Measuring a couple of blood glucose concentrations during the day under the assumption that glargine is peakless can create real problems when the insulin is not peakless in that particular cat. You will misinterpret your results if you assume that the glucose concentration is a flat line. That can lead to overdose and the Somogyi effect. I think glargine is a useful insulin, but don't assume that the blood glucose concentration is not fluctuating, especially if the cat is poorly-controlled.
Dr. Scott-Moncrieff: Another issue with glargine is that sometimes the blood glucose nadir occurs right before the next injection. So veterinarians measure a normal blood glucose concentration when the patient is ready for its next injection, and they worry that the patient may become hypoglycemic if they give another dose of insulin. I would recommend continuing the curve, and if the blood glucose nadir occurs at the time of the next injection this is acceptable as long as the cat is not hypoglycemic.
Dr. Ford: So, Dr. Nelson, are you suggesting that with glargine we should check blood glucose for a curve every two hours rather than every four hours?
Dr. Nelson: If the cat is not doing well, you have to check the blood glucose concentration more frequently than every four hours. You have to figure out what the insulin is doing and identify the low point. If your patient's blood glucose concentration is decreasing and it's 6:00 p.m. and you haven't identified your nadir, call the owners and tell them you would like to keep the animal overnight. At 8:00 p.m., when the cat is due for its next insulin injection and food, feed it but don't give it the insulin and then check the blood glucose a couple of hours later. If the blood glucose spikes up, the insulin is gone. If the blood glucose is not increasing, you still have circulating insulin.
Dr. Scott-Moncrieff: For cats being treated with glargine, the blood glucose concentration can be in the well-controlled range right before the next injection and that may not be a problem. It could be in the 80- to 120-mg/dl range right before the next injection and that could just reflect good control. Whereas with other insulins, the blood glucose concentration tends to be the highest right before you give the next dose.
Dr. Norsworthy: If you are starting with a newly diagnosed diabetic cat, do you consider how high the blood glucose concentration is when choosing an insulin dose?
Dr. Nelson: No, I start with one unit of PZI twice a day and go from there. I am trying to avoid having symptomatic hypoglycemia occur at home in the first week or two. The owner is dealing with handling the syringes, drawing up the insulin, understanding the treatment protocol, and more. The last thing I want is the animal to become hypoglycemic. So I always start conservatively. If I feel the diabetes is not controlled, I will adjust the dose within a week, usually at five to seven days. If the owner is reporting improvement and the cat is eating a high-protein, low-carbohydrate diet, then I will let it go a little longer. I tell most of my clients that it will take about a month, whether their cats are newly diagnosed or we're trying to regain control.
Dr. Peterson: I think we are all saying one to two units of PZI twice a day and then we check them in the first week and make adjustments. We've agreed for 20 years that once a day is not going to do it.
Dr. Ford: If you were going to change a cat from glargine to PZI, where would you start?
Dr. Nelson: I usually start at one unit per cat twice a day.
Dr. Scott-Moncrieff: In the original PZI study, there was no correlation between weight and dose to control diabetes. There were some heavy cats in the study that became hypoglycemic on low doses.
Dr. Edlin: How do you handle the transition from Lente insulin to ProZinc? If you have a cat on three units twice a day of Lente insulin, do you dare go to three units of ProZinc?
Dr. Nelson: I would start all over again at one unit twice a day. It is unpredictable what the difference between the two insulin products will be. There is individual variability in cats, and you can't predict how they are going to respond. The only exception is the transition from PZI Vet to ProZinc; this is easier than with other insulins because they are comparable products. The other insulins are completely different in their pharmacodynamics.
Dr. Ford: I want to bring up the topic of compounded insulin. What do you think about using it?
Dr. Scott-Moncrieff: I don't use it based on my clinical observation that cats are often poorly regulated on compounded insulin. They improve when we switch them to a commercially available insulin. We just finished a study evaluating a variety of compounded insulins from a variety of different sources, and the variability is incredible. The products varied in factors such as pH, zinc concentration, and potency—not only from product to product but even within the same product. With ProZinc, the insulin is complexed to protamine and zinc in the supernatant, but with some of the compounded insulins, most of the insulin is free in solution. That means you are not giving PZI; you are giving predominantly regular insulin.
Dr. Ford: Do you think compounded PZI came about because ProZinc wasn't available? Now that ProZinc is available and everybody likes PZI, do you think the compounded insulin will no longer be in demand?
Dr. Peterson: No. It's about getting the PZI cheaper. Unfortunately, compounded PZI is not going to go away despite the fact that these insulins are not reliable.
Dr. Nelson: The bottom line on compounded insulin is there is no oversight and you don't know what you are getting. I can't afford to not have product consistency. I'm trying to figure out why that animal is not well-regulated. I need a reliable product.
Dr. Ford: What about dietary considerations in managing the diabetic cat?
Dr. Kirk: I think you can regulate a cat on any diet, with the exception of the diet high in simple sugars. I typically use a low-carbohydrate pet food in newly diagnosed diabetic cats. The purpose of dietary control is to slow glucose absorption and avoid blood glucose peaks. I think there are two main dietary strategies: You can feed fiber and slow glucose absorption across the bowel or you can feed a pet food with low glucose so they only get glucose through hepatic gluconeogenesis. I will allow cats to eat free-choice if they are not obese. But most of them are obese males so you have to control the amount they eat to achieve weight loss. If a cat is overweight, I recommend weight loss while I am regulating it, at least after the first week of insulin therapy. With very obese cats, I use a high-fiber formula because the amount of food these cats need to achieve weight loss is so small that the owners can't deal with the small food volume that would be required using a low-carbohydrate food. The increased amount of food in a high-fiber pet food improves satiety, and the owners' sense of food volume. If a cat is not obese or won't overeat, I'll choose a low-carbohydrate food. I think canned food is helpful because it reduces over-consumption. In nonobese cats, we often continue their current diet, or we may choose a therapeutic food, especially if they are poorly regulated.
Dr. Nelson: One recommendation is that diabetic cats should not be fed dry pet food, period. It's so easy to throw more dry food in the bowl, whereas with a can the amount fed is more controlled.
Dr. Edlin: I don't usually change pet food until about three weeks after starting insulin therapy; I want to see that the insulin works first. And if the cat is a newly diagnosed diabetic, it may have experienced pancreatitis at the same time. Do you want to change the diet and exacerbate the pancreatitis?
Dr. Norsworthy: I run a pancreatic lipase immunoreactivity test on all my newly diagnosed diabetics. I realize it doesn't absolutely correlate to chronic pancreatitis, but that is the best test currently, short of ultrasonographic examination by a very experienced ultrasonographer.
Dr. Scott-Moncrieff: I change their diets right away; I don't worry about pancreatitis unless they have clinical signs that are suggestive of pancreatitis. What to do in the cat being fed a therapeutic pet food for another disease is a different issue. In that situation I tend to leave the diet alone.
Dr. Nelson: That is where I shy away from the high-protein, low-carbohydrate diet, especially if I think renal insufficiency may be an issue. Interestingly, in the recent PZI study, we did not put the cats on a specific pet food; the majority of the cats were just on regular cat foods, and the overwhelming majority of the cats did well.
Dr. Kirk: That's great if they are regulated. When they are not regulated, therapeutic pet food is advantageous.
Dr. Ford: Let's discuss monitoring diabetic cats now. My clients do a lot of home blood glucose monitoring. In the first week, we have them monitor blood glucose concentrations every 12 hours before each canned food meal. The cats are typically rechecked in five to seven days. If the at-home monitoring is going well and if a cat is a candidate for diabetic remission, we suggest monitoring four times a day if the owner is able. We have the owner monitor four times a day for four to six weeks until we achieve diabetic remission or until it is clear remission is unlikely. If the cat is going into remission, monitoring is tapered off from twice a day to once a day to two or three times a week to once a week or any time we are concerned about a relapse when clinical signs reappear.
Every one to three weeks I have owners fax me their cats' blood glucose concentrations for the week. It is a teaching point for the interns and residents to look at the glucose concentrations. Then my assistant e-mails the owners. That is how we keep on top of it. If owners don't fax the results for a month, we call them. I also ask clients to bring their cats into the hospital every three to four months to be weighed and to talk about how they are doing. Then I ask owners to do a blood glucose curve at home once a month. I tell them that we are a team. And if they think their pets are not doing well enough and they want to change the dose, then please call me and tell me what adjustment they would like to make. I may want to adjust the dose differently.
I want to ask the panel about your experience with owners. Do they change their cats' insulin doses frequently?
Dr. Peterson: Yes, but I prefer they call or e-mail me first, and they usually do. I would rather know their cats' status and discuss it. I ask owners to e-mail the blood glucose curves to me. I interpret the curves, comment on them in the patient record, and then make my recommendation.
Dr. Nelson: I only recommend doing a blood glucose curve if the cat is poorly regulated. I base my control more on history and physical examination findings and stability of body weight. If everything looks good—no signs of hypoglycemia and the cat is jumping normally, then I don't recommend doing a curve. I periodically have the owner monitor two or three blood glucose concentrations during the day to be sure the blood glucose is staying between 100 and 300 mg/dl, and that's it.
Dr. Scott-Moncrieff: I use blood glucose curves as one more piece of information to add to the weight measurement and clinical signs. I see a lot of cats with asymptomatic hypoglycemia, so even cats that appear to be well-controlled should be seen every three months for a glucose curve. In some cats, we can't interpret in-hospital curves because every time the cats come in, they flip out and you know you won't generate good information. In this situation, I use fructosamine concentrations and in-home glucose curves (if feasible) to assess glycemic control.
Dr. Edlin: I think a lot of general practitioners are using in-home glucose curves, but many still do in-hospital curves and fructosamine measurements.
Dr. Ford: Do all of you check fructosamine concentrations?
Dr. Edlin: We use fructosamine measurements initially and with almost every treatment change. If we change the diet then we will check fructosamine concentrations a month later.
Dr. Nelson: The value of fructosamine is not in the one-time measurement, but in the changes over time. I always check the fructosamine concentration in poorly regulated cats because you never know when you'll need the next one. It's especially useful where stress hyperglycemia is an issue.
Dr. Norsworthy: That's when I use it. When I try to differentiate stress hyperglycemia from true hyperglycemia.
Dr. Scott-Moncrieff: Fructosamine concentrations are most useful in well-controlled cats. Most of the diabetic cats I see are poorly controlled. I don't need fructosamine to tell me that they are poorly controlled because they are losing weight and are polyuric and polydipsic. It is useful in cats that you think are doing well. In these cats, I would rather check blood glucose concentrations in combination with fructosamine than do the blood glucose alone.
Dr. Peterson: I would not depend on fructosamine alone as a monitoring tool. Rather, I use this test as part of the overall home-monitoring strategy, which includes clinical signs (water consumption and urination, appetite, and body weight), as well as urine glucoses or home glucose monitoring or both, if possible.
Dr. Ford: What other monitoring strategies do you use?
Dr. Kirk: Some clients don't feel like they can monitor blood glucose at home. For those clients, we send home urine glucose strips for the litter pan. These clients use them to check for prolonged hypoglycemia to make sure their cats are not transitioning out of diabetes. If the cats have no glucosuria for three days in a row, then we are either dropping their blood glucose concentration too low or they are going into remission.
Dr. Nelson: Detecting urine ketones can help you in the other direction. For example, in obese newly diagnosed diabetic cats being given glucocorticoids, you might just put them on a high-protein, low-carbohydrate diet and see what happens over two weeks. If they start having ketones in their urine, you have to start insulin therapy. If they become negative for urine glucose, maybe you can control them with diet alone.
Dr. Kirk: But some practitioners say they never look at urine glucose strips because they don't provide any information.
Dr. Nelson: These strips are more useful in cats than dogs because cats can go into diabetic remission and dogs don't. So in a cat, especially in the early stages, urine glucose strips can be useful.
Dr. Scott-Moncrieff: The main thing I use the urine glucose strips for is if I am not sure the cat is truly diabetic, I use the strips to help figure out whether the blood glucose concentration is elevated due to stress hyperglycemia. Certainly I can use fructosamine concentrations for that purpose, too. But if a hyperglycemic cat is persistently glucosuric in an unstressed home environment, then I'll start treating it for diabetes. If it isn't glucosuric at home, then I may just change its diet.
Dr. Peterson: Whenever I can, I have owners measure water intake with a measuring cup. They can do that fairly easily if they only have one cat. It can be very helpful in the overall regulation of a cat's diabetes. It makes the owners (and the veterinarian) feel good because they are measuring something. They're not just saying, "Oh, I think he's drinking less." They know the cat is drinking less. If the cat starts to drink more, you get it in the hospital and do a blood glucose curve.
Dr. Norsworthy: Another thing that clients can do to monitor at home is to weigh the cat. The owner can easily weigh the cat at least twice a week, and that's an excellent indicator of a diabetic cat's condition in a multi-cat household in which monitoring for food and water consumption and urine output may be impossible.
Dr. Scott-Moncrieff: It comes back to the principle of not looking at just one parameter, whether it is blood glucose or fructosamine concentrations. You have to put them all together and get a holistic idea of how well the cat is doing.
Dr. Ford: Initiating insulin therapy in diabetic cats reverses glucose toxicity. Once the blood glucose concentration is lower, many cats will regain insulin secretory ability. In-home blood glucose monitoring is not for every cat or cat owner. Owners who are proactive and willing to monitor blood glucose concentrations at home have an increased chance of diabetic remission in their cats, especially if the cat was given glucocorticoids in the recent past. The challenge is to implement a treatment protocol for cats that the owners are willing and able to comply with.
Dr. Ford: Now let's discuss the protocols we use so our clients will have successful outcomes with their diabetic cats. I usually ask clients at the very beginning if they are interested in monitoring blood glucose concentrations at home or if that is too much for them right now. I let them tell me what they want to do. I don't want to push too hard because then they are not going to do anything that I recommend. If they are going to do in-home monitoring we also send them to the Web site AbbottAnimalHealth.com for more information. I have a discharge handout on diabetes and a list of recommended pet foods with the carbohydrate, protein, and fat contents included. The handout includes a picture of the pancreas because I usually explain pancreatitis to both dog and cat owners. Also included is a log for the first week, including monitoring blood, urine, or just clinical signs if they are not on board with doing home testing yet. I also review the clinical signs of hypoglycemia and the use of Karo® syrup before they leave. My goal is regulation and, in some cases, remission. I talk to them the next day to see how they are doing and if they have any questions. Usually they return in a week. In the interim, we make another phone call to see how they are doing.
Dr. Norsworthy: At the time of diagnosis, I do a urine culture and a pancreatic lipase immunoreactivity test. I look for periodontal disease, and if it's present we clean the teeth within the first three weeks of treatment. I have a 10-page handout for every client with a newly diagnosed diabetic cat, and http://ProZinc.us has some great educational videos to help reinforce my recommendations to clients.
In these cats, we immediately start a low-carbohydrate diet. I prefer canned cat food, but if the cat is eating dry cat food I send canned food home and recommend the owner feed at least some of it if possible. Consistency is a big issue: the same insulin and the same food and volume at the same time every day. I check the patient's blood glucose concentration after the initial diagnosis once a week 12 hours after insulin administration until the cat is regulated. Each of my exam rooms is computerized, and there is an electronic template for the diabetic recheck.
At each recheck, my technician weighs the cat and compares the weight to the last week's weight and asks questions about water intake, urination, and appetite. We ask how the cat is feeling, which I think is an extremely important question even though you get somewhat subjective answers. Then we check the blood glucose concentration and interpret the value in light of the clinical signs. You shouldn't put all of your emphasis on glucose measurements. I don't routinely recommend in-home glucose monitoring, and I haven't performed a glucose curve in more than 10 years. You have to look at the big picture. For cats that are regulated, I recommend a recheck every two to three months. Their owners weigh the cats weekly or every other week and watch for significant changes in clinical signs. We treat most diabetic cats for years like this; they typically receive 2 or 3 units of PZI twice a day.
Dr. Ford: What do you think your remission rate is with that protocol?
Dr. Norsworthy: I have about a 25% remission rate. And it is higher for the cats that eat the canned low-carbohydrate cat foods.
Dr. Ford: Is remission a realistic goal in some percentage of cats?
Dr. Nelson: I never talk to clients about remission as a goal. My goal is to get the cats as well regulated as possible, and if they undergo remission, then great. When you understand the underlying issues related to beta cells and insulin resistance, you know there are a lot of variables. It's not just about putting them on a low-carbohydrate pet food.
Dr. Kirk: I discuss the possibility of remission—that one-third of diabetic cats may go into remission. I talk about the fact that cats may go into and out of remission, and just because the diabetic condition goes away doesn't mean it will stay away. We start with diet and optimal weight control being important along with glucose regulation and avoidance of hypoglycemia.
Dr. Ford: Let's examine the more challenging scenarios involving diabetic cats; for example, the diabetic cat with ultrasonographic evidence of an inflamed edematous pancreas. It is anorectic and hyperglycemic and has decreased gastric and duodenal motility. How would you approach this case?
Dr. Nelson: Well, if the cat is anorectic, I would hospitalize it, administer intravenous fluids, and control hyperglycemia with regular insulin as needed. If clinical signs are severe, I would withhold food for 24 to 48 hours and then feed either a highly digestible diet such as Purina EN® (Société des Produits Nestlé S.A., Vevey Switzerland) or a diet with a moderate increase in mixed fibers such as Purina OM® (Société des Produits Nestlé S.A., Vevey Switzerland). I also use prednisolone at a dose of 2.5 to 5 mg per day for one or two weeks to help control inflammation. Some cats will go into diabetic remission as the inflammation is controlled. Chronic recurring pancreatitis is a common cause of recurring symptomatic diabetes in cats.
Dr. Norsworthy: I agree. Low-dose prednisolone is my preferred treatment, and I've had cats go into remission while they were on it.
Dr. Nelson: Gingivitis is another important problem that can interfere with diabetic control. Inflammatory mediators can cause insulin resistance, so you need to treat infections and control inflammation as much as possible.
Dr. Ford: Do you use clindamycin in diabetic cats with gingivitis?
Dr. Nelson: You can treat them with clindamycin. My experience is that if you clean their teeth and treat the infection, their insulin sensitivity improves. This has been well-documented in people.
Dr. Kirk: With the knowledge that obesity is a chronic inflammatory disease, do you think we underestimate the importance of returning a cat's body weight to normal?
Dr. Nelson: No, I think most veterinarians understand the interplay between obesity and diabetes. If you are treating an obese cat with diabetes, you have to focus on returning that cat to a target body weight and then keep it there. One of the markers of a well-controlled diabetic is a stable body weight once an ideal body weight has been attained.
Dr. Edlin: We need to establish the insulin protocol and get blood glucose concentrations under control and then work on weight loss.
Helpful Feline Diabetes Web Sites
Dr. Scott-Moncrieff: And it is different when you are dealing with a sick diabetic cat. Your first priority is to get that cat eating and feeling better. At that point you are not worried about weight loss. A stable cat that is feeling well is a different issue.
Dr. Kirk: My concern is the number of cases where the diabetes becomes the total focus of care. It is easy for weight loss to get sidelined. Often we don't recognize that the potential for improved glycemic control and remission increases if the obese cat loses weight.
Dr. Ford: Let's discuss another important topic. How do we get the other members of our veterinary healthcare team on board as far as client education goes? They need to educate owners on giving insulin injections, feeding the appropriate pet food, and monitoring the pet, and they need to be encouraging and convey that diabetes is a treatable disease.
Dr. Edlin: Once the client leaves the hospital, the veterinarian is already moving on to the next case. Communication is very important over that next week.
Dr. Ford: Does your healthcare team call owners to see how patients are doing, and do owners fax blood glucose results in?
Dr. Norsworthy: I schedule rechecks on a weekly basis until the cat is regulated. We have time set aside for the staff to call clients to remind them of their rechecks. If a patient's condition has changed or if clients are reluctant to come in for a scheduled recheck, the team reports that to me.
Dr. Edlin: Although the general population has heard of diabetes, I don't think they understand the pathophysiology and how insulin works. It is a lot of information for owners to comprehend, and they forget much of it.
Dr. Norsworthy: That is why I have handouts.
Dr. Kirk: There are written instructions on how to give insulin injections on MyCatHasDiabetes.com, and educational videos on http://ProZinc.us along with information on how to monitor at home. In addition, I ask my clients to keep a diary to record the results of their blood glucose and urine glucose or ketone monitoring.
Dr. Ford: Do you have any other suggestions for the healthcare team to make it all work?
Dr. Edlin: Obviously follow-up communication is one of the most important aspects of successful diabetes management. No matter what we send home with our clients, not everything is going to be read or understood. You need to call them the next day, just to see how their first injection went. And be sure to have them return the next week.
Dr. Ford: This has been an excellent discussion. Are there any parting comments or thoughts?
Dr. Edlin: I think the general practitioner is often worried about the client costs of treating diabetic cats. However, the result of using suboptimal insulin is increased expense because diabetic control is compromised.
Dr. Scott-Moncrieff: The other big take-home message today is the importance of the veterinary team. The veterinarian, veterinary technician, and owner need to work together to ensure a successful outcome for the diabetic cat.
Dr. Peterson: I think one of the biggest things we all agree on is that ProZinc is a very good insulin, especially over the compounded products. I also like the fact the Boehringer Ingelheim is a company that is supporting veterinary medicine and supporting us.
Dr. Kirk: In working with various endocrinologists on dietary studies for diabetes, I've observed that some of the dietary considerations don't make as much definitive difference as you would think: for instance, the low-carbohydrate vs. high-carbohydrate diet. In many cases, all the cats improved when they entered the studies because of the optimal level of monitoring and oversight during the clinical trials. What that tells me is that I am slacking off on my monitoring and follow-up or I am not convincing owners to be as proactive as they should be. It means we all need to pay better attention to overall case management.
Dr. Ford: Feline diabetes is a dynamic disease with variable complicating diseases and outcomes. As diabetologists, we are very pleased to have ProZinc as a therapeutic option in the treatment of feline diabetes. The quality of life for some percentage of the diabetic cat population will definitely benefit.
1. Lue, TW, Panternburg, DP, Crawford, PM. Impact of the owner-pet and client-veterinarian bond on the care that pets receive. J Am Vet Med Assoc 2008; 232(4):531-540.
2. Nelson, RW, Lynn, RC, Wagner-Mann, CC, Michels, GM. Efficacy of protamine zinc insulin for treatment of diabetes mellitus in cats. J Am Vet Med Assoc 2001; 218(1):38-42.
3. Nelson, RW et al. Field safety and efficacy of PZIR for treatment of diabetes mellitus in cats. J Vet Intern Med 2009; 23:787-793.
4. Norsworthy GD, Lynn R, Cole C. Preliminary study of protamine zinc recombinant insulin for the treatment of diabetes mellitus in cats. Vet Ther 2009; 10:24-28.
Supported by an unrestricted educational grant of Boehringer Ingelheim Vetmedica, Inc.
As a class, the use of any insulin when regulating a diabetic cat may be associated with side effects. The most common side effect reported in field studies was hypoglycemia. This is usually mild (lethargy, weak, trembling, uncoordinated, groggy, dazed) but may be serious and life-threatening (seizures, coma).1-2
If side effects occur, cat owners should contact their veterinarian immediately.
1FOI for NADA 141-297. (PROZINC)
2PROZINC Product Insert
Vetsulin is a registered trademark of Intervet/Schering-Plough Animal Health or an affiliate.
Karo is a registered trademark of ACH Food Companies, Inc.
Purina EN and Purina OM are registered trademarks of Société des Produits Nestlé S.A. Vevey, Switzerland.
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