VetInfo Digest     June 1998

This issue
When Good Medications Do Bad Things
What do all those blood values really mean?
Pre-Operative Sedatives, Analgesics and Anesthetics
Pain Relief for Pets
Corticosteroid season
Quick Tips for Summer Travel with Pets
 
 

When Good Medications Do Bad Things

There are a number of medications which are very helpful for most pets but which make a few pets ill or even cause death in extreme instances. Using these medications is often necessary in spite of the possible side effects, especially when there are no other medications for a condition. In other cases, the beneficial effects may justify some risk taking even with serious potential consequences. Being aware of the potential for danger can help to prevent problems or to allow a pet owner or veterinarian to catch them early enough to reverse problems induced by the medications.

The ultimate example of a medication that has harmful side effects but is essential for life, at least in diabetic pets, is insulin. Even a small overdosage can have serious consequences and strict monitoring of the medication is essential. Despite that, there are few calls for it to be removed from the market. Why? Because the benefit clearly outweighs the risk. Where there is no other choice a huge risk is worth taking. For most other medications the risk to benefit picture isn't quite so clear.

Antibiotics are often harmful to patients. Sulfa/trimethoprim (Bactrim Rx, Tribrissen Rx, Ditrim Rx, Sulfatrim Rx, SMZ-TMP, other generic names) is an antibiotic that can cause joint inflammation in Dobermans and is implicated in immune mediated thrombocytopenia (ITP) in many dog breeds. Thrombocytes are the platelets in the blood, responsible for blood clotting. Thrombocytopenia is a decrease in the number of platelets. Obviously, if they get low enough there is a great risk to the pet. This antibiotic is still widely prescribed, though. It has a broad spectrum of action, it is inexpensive and most of the time it doesn't cause problems. The ITP is almost always reversible if the medication is withdrawn. Remembering that this antibiotic can cause this problem may help to save your pet's life, though. Penicillins can cause severe allergic reactions, even causing sudden death in a few patients. Many antibiotics cause diarrhea. Chloramphenicol has been associated with aplastic anemia in several species. Enrofloxacin (Batyril Rx) and tetracycline antibiotics should not be given to growing pets unless absolutely necessary due to the potential for problems with absorption of the medications into bone and/or teeth, causing defects. Amikacin and gentamicin are aminoglycoside antibiotics. This group of antibiotics can cause deafness and kidney failure. Use of antibiotics should be restricted to conditions which are likely to respond to appropriate antibiotic therapy since these are not harmless medications. When they are necessary it is obvious that some risk of use is justified.

Heartworm preventatives often come under scrutiny by pet owners when a pet suddenly dies or develops an illness that may be associated with drug reactions and the only medication the dog is taking is the heartworm prevention medication. Filaribits Plus (Rx) can cause an idiosyncratic (we don't know why it happens) liver reaction in a small number of dogs. Dobermans seem to react more commonly to this medication than other breeds, too. There are alternative heartworm preventatives, so it is possible to use another medication if reactions occur. The newer monthly heartworm preventatives are often suspected of being the cause of the problem when immune mediated hemolytic anemia occurs in dogs but there is no proven connection that I am aware of. About half the cases of immune mediated hemolytic anemia (IMHA) occur for no apparent reason but the most commonly identified reason is probably reaction to an administered medication. Therefore, people are suspicious of the monthly heartworm preventatives when IMHA develops in their pet. Heartworm is a devastating disease and if you live in an area in which it occurs it is essential to use the best medications to prevent it. For most people this is one of the monthly pills (Heartgard Rx, Interceptor Rx and ProHeart Rx). Don't risk heartworm disease in your pet because you run across suggestions of danger on newslists or from other sources.

What about situations in which there is very little risk of death from a condition but there is a great deal of suffering associated with it, or when a medication is used to lessen the stress and anxiety of surgery or examination procedures?

The newest example of a medication with peculiar side effects in a small number of pets is carprofen (Rimadyl Rx). This medication is very effective at controlling pain and allowing dogs with arthritis to move comfortably again. It is safer than most medications in its class for use in dogs since it is much less likely to cause ulcers than other non-steroidal anti-inflammatory (NSAID) medications approved for use in dogs. However, it can cause toxic liver reactions in a few dogs. At the present time the majority of dogs affected in this manner have been Labrador retrievers but other breeds have been affected. There are a small number of confirmed cases of problems and a large number of dogs on this medication so the problem seems to be rare but definitely real. If your dog is on Rimadyl and you see any signs of inappetance, lethargy, vomiting or ill health in general, please contact your vet. Checking to see if there is evidence of liver damage would be a very good idea if any reaction to this medication occurs and it may not be a bad idea to just routinely run tests for liver enzymes a few days to a few weeks after starting Rimadyl. In any case, don't simply assume that whatever is wrong will get better in a few days and keep giving the medication. Stop, call your vet and inform him or her of the problem. Rimadyl is a very good medication and I have used it in one of my own dogs. Just be aware of the potential for problems.

Acepromazine is frequently used by veterinarians to lessen the stress and anxiety associated with anesthesia and for other beneficial effects in anesthetized patients. There are a few reports of serious side effects in boxers. It can also lower the seizure threshold and should not be used in pets known to have seizure disorders. Make sure that the vet or the veterinary assistant notes on the record or admission form that your pet suffers from seizures before a surgical procedure, just in case your vet uses this medication as a standard part of the anesthesia protocol.

There are other peculiar drug reactions and other medications with side effects. We are going to cover the side effects of corticosteroids later in this newsletter and hope to continue to keep you informed of potential problems with medications in future issues. Good medications must still be used carefully.
 

What do all those blood values really mean?

Over the next couple of months we will try to explain what many of the blood values from routine veterinary tests mean. We draw blood from pets almost every day and we dutifully report the results to the owners. In our practice we try hard to inform pet owners of the meaning behind various lab tests but we do not explain each test in depth very often. It is a good idea to know what the pitfalls are with any test and especially with tests in which the outcome may influence treatment decisions and possibly even life or death of a pet.

There are a number of blood tests done that seem to have very straightforward results. These are the tests that have either "positive" or "negative" for a value. If the test methods were 100% accurate these would be simple tests to understand. Unfortunately it is pretty rare for a test to work that well.

The best example of this kind of testing in veterinary medicine is heartworm testing. Heartworms have a very complicated life cycle which makes testing for infection more difficult than you might imagine. The original test for heartworms was simply to put a drop of blood on a slide and look for microfilaria, which are the microscopic babies produced by adult heartworms. When dogs are infected with heartworms it is not unusual to find several microfilaria in a single drop of blood -- in every single drop of blood examined. As long as there are both male and female heartworms in the heart or pulmonary vessels it seems logical that there would be baby heartworms. It is immediately apparent that there are several conditions which would produce false negative results when looking at a drop of blood, though. First, there may only be male or only be female heartworms. Secondly, the heartworms have to be adults in order to produce babies. There may not be enough baby heartworms for each and every drop of blood to have at least one baby worm. It takes about 6 months for heartworms to mature into adults so any infections of all pre-adult worms would not be found in this manner. There is even a microfilaria disease (Dipetelonema) that is not from heartworms in some areas of the country, so if microfilaria are found they need to be clearly identified. Finally, some dogs have the ability to kill off the baby heartworms in their circulation even though they can not kill the adult heartworms. I have not found a really well documented percentage for false negative results looking directly at blood but a reasonable estimate is that this test misses 40% or more of heartworm infections. To try to increase the accuracy several methods of concentrating the baby heartworms from larger volumes of blood were developed. These helped to solve the problem of finding microfilaria when there were only a few in the dog's system but didn't help much with the other testing problems. More recently "occult" heartworm testing has been developed. These are tests which detect the antigen (part of the worm) from adult female heartworms. These tests still have some of the problems of the original tests in that they don't detect pre-adult infections and they only detect female heartworms so all male infections will go undetected. In addition, the tests are a lot more complicated and there are now cases of false positive and false negative tests that occur because of the test itself instead of just happening due to its limitations. The rate of false positives and false negatives varies a little bit from test to test but in general occult heartworm tests give false positive results about 1 to 4 times per 1000 tests and false negative results a little more frequently than that. In an area like coastal Virginia, where I practice, a "positive" test is much more likely to be an actual heartworm infection than in an area like Utah were heartworms are not nearly as likely. If the infection rate in dogs is less than 1 in 1000, it is more likely that a positive test result is a false positive than a "real" positive. It is a good idea to use more than one testing method in any dog in which a positive heartworm test occurs when there are no clinical signs of the disease, especially in areas in which heartworms are not likely. In cats the situation is even more complicated. Cats are much less likely to have microfilaria in their blood and they often have so few heartworms that detection of them can be difficult even with occult heartworm testing. There are blood tests for antibodies to heartworms that are used in cats but it is important to understand that a test for antibodies only indicates exposure to heartworms, it does not confirm an active heartworm infection. It can be pretty hard to actually confirm heartworms in cats but they do sometimes show up on ultrasound exams and if there are clear clinical symptoms and a positive antibody or antigen test it is reasonable to assume that an infection is present.

Feline leukemia virus is also very complicated to test for. The currently available tests detect the virus particles directly, so this is an "antigen" test. That is good, because it is more reliable than antibody testing. The result is either positive; antigen is found, or negative; the virus is not found in the blood stream (or tears or saliva). The problem with this test is that feline leukemia virus can hide in the bone marrow or in the central nervous system and not be in the bloodstream. For a long time veterinarians have known that many cats which test positive for feline leukemia will test negative three or four weeks later. We assumed that these cats were capable of fighting off the virus and were thus immune to infection. More recently, the phenomenon of latently infected cats has been recognized. These are cats which are capable of keeping feline leukemia virus suppressed and inactive but not capable of clearing it from their bodies. A significant stress later in life may allow the virus to be reactivated. They test "negative" on a blood, saliva or tear test but actually are infected. Knowing that this occurs makes it harder to rely on a "negative" test value for feline leukemia virus but at least these cats are not too likely to infect another cat and usually do well despite the infection. What about cats that test consistently positive? These are the carrier cats, capable of infecting other cats. So we still recommend testing cats for feline leukemia at least twice if they test positive on the first test. If they subsequently test negative we cross our fingers and hope that they live out normal lives, either free of the virus or successfully suppressing it. If they test positive twice, at least three to four weeks apart, we suspect they will be lifelong carriers and capable of infecting other cats. This means a lot of changes in lifestyle and indicates a need for aggressive treatment of any condition causing the cat to appear ill since these are the cats which usually have a shorter lifespan due to the feline leukemia virus.

Feline immunodeficiency virus infection is another disorder we test for with a positive/negative test. This test is an antibody test, so it only indicates whether a cat has been exposed to the virus. Since exposure sufficient to produce antibodies normally indicates infection this test works a little better than antibody tests normally work. However, young kittens may receive antibodies in the milk from their mother but not be infected, so any kitten less than 6 months of age with a positive FIV test should be retested after it is at least 6 months old. Also, there is a latent period, just like with human immunodeficiency virus (HIV) of several months after infection before the body starts to produce detectable antibodies. So a cat known to be exposed to the virus should probably be retested several months (four to six) after the exposure occurred. Finally, there are a few false negative tests and less commonly false positive tests for this condition. Cats with FIV can live nearly normal lifespans, so a positive test should not be taken as a death sentence.

Next month we'll try to cover complete blood counts and then move on to serum chemistry tests in the months ahead. If there are specific tests that any of our subscribers have an interest in, please feel free to let us know at digest@inna.net or mervet@inna.net. If you write, please mention that you subscribe to VetInfo Digest.
 

Pre-Operative Sedatives, Analgesics and Anesthetics

There are several classes of drugs used to induce anesthesia or control pain in dogs and cats.

Pre-operative sedatives and tranquilizers are used to reduce the excitement and stress that often accompany anesthesia. They often make it possible to use lower dosages of the anesthetic agent which increases the safety margin of the procedure. The most commonly used pre-operative sedative is probably acetylpromazine (Acepromazine, PromAce Rx). It is usually used in dosages

that are much smaller than the standard label dose. It is considered to be a very safe medication but there are have been anecdotal reports of severe reactions to this medication in boxers. It can make it easier for seizures to occur in dogs that are prone to seizure episodes so it is important to

remind your vet that your dog has seizures, especially in an emergency situation in which this information may not be readily available. An alternative medication that is used frequently in cats but less frequently in dogs is diazepam (Valium Rx). Xylazine (Rompun Rx, others) is also used

by many veterinarians. It is a much more potent sedative but it has depressant effects on the respiratory and cardiovascular systems that make it a little less safe. Medetomidine (Dromitor Rx) is another sedative agent that is similar or greater in potency than xylazine and has a specific

antagonist, atipamezole (Antisedan Rx), that can be used to reverse its effect. It also has stronger respiratory and cardiovascular effects than acetylpromazine but may be a good choice for short manipulative procedures or short surgical procedures that are not especially painful.

Pre-operative sedatives are often combined with analgesic medications. Analgesics are medications which relieve pain. Many of them also have some sedative effect. Common combinations of sedatives and analgesics in veterinary medicine include acetylpromazine and butorphenol (Torbugesic SA Rx) or acetylpromazine and oxymorphone. These combinations can be especially important when isoflurane gas is used as the anesthetic agent because it has very poor residual analgesic effect. An animal anesthetized with isoflurane may experience a sudden rush of pain post-surgically as the anesthetic wears off if an analgesic is not administered at some time prior to or during the surgical procedure. The combination of a pre-operative sedative, an

analgesic and a local anesthetic agent is also very effective for many procedures such as removal of tumors from skin or biopsy procedures. With spinally administered local anesthesia these medications may even allow completion of more complex surgeries such as cesarean sections. In general, pre-operative sedation and administration of an analgesic agent is a good idea and is worth considering in most circumstances.

Anesthesia is considered to be the loss of sensation. In local anesthesia the loss of sensation is confined to a portion of the body. By injecting local anesthetic agents under the skin, a very small area of the body can be anesthetized. By injecting an anesthetic agent into the spinal canal a much

larger portion of the body can be anesthetized, but the anesthesia is still considered to be "local", even though both rear legs and most of the abdomen may lack sensation. When the loss of sensation also involves the loss of consciousness and motor function the patient is in "general anesthesia". To make things a little more confusing, there are several "stages" of general anesthesia which describe the process the brain is going through. The first plane is loss of consciousness. The second is a stage of "excitement" which occurs during the period from loss of consciousness to loss of motor function. If stage two anesthesia is prolonged there may be visible

movement, whining or vocalization and the patient can appear to be in pain or delirious. Stage three anesthesia is the "surgical level". At this point the muscles are relaxed enough to allow surgery and there is a total loss of consciousness. This stage of anesthesia is further divided into four "planes". The first is plane is loss of eyelid reflexes, the second the loss of eye movement entirely, the third is a noticeable decrease in respiratory effort and the fourth is purely diaphragmatic respiration. If anesthesia is allowed to progress to stage four there is loss of respiratory and cardiovascular function, leading to death.

There are a number of general anesthetic agents in use in veterinary medicine today. There are a number of ways to break anesthetic agents into classes but the most confusing to pet owners is probably the use of anesthetic induction agents and anesthetic maintenance agents.

Induction agents are used because the best maintenance anesthetics are the gases. The problem with gases is administration. Many pets will not tolerate breathing anesthetic gases even with preoperative sedation. It is very hard to place a mask over their noses and expect them to hold still and breath in a gas until they are unconscious. It just goes against all natural tendencies. On the other hand, injectable medications used for anesthesia can not be withdrawn once they are administered and it is hard to fine-tune the dosage to the patient's needs. So vets do not like to use long-acting injectable anesthetics if it is possible to avoid them. The compromise is to use a short-acting injectable anesthetic to make the pet unconscious and allow placement of a breathing tube for the gas. These short-acting agents are called anesthetic induction agents. Sodium thiamylal and sodium pentothal are barbituate induction agents. They are quick acting and gentle

for the pet, because the anesthesia they induce sets in before there is a struggle. They are among the easiest anesthetic agents to overdose because individual susceptibility to their effects varies widely. These are the anesthetic agents most responsible for the fear of "anesthetic sensitivity" since some pets really do seem to be so sensitive to them that they will die from doses low enough that they would usually be very safe. Many vets are reluctant to give up the quick induction of anesthesia, which results in a more pleasant experience with surgery for most patients, despite the potential for occasional deadly reactions. The barbituates can be used alone as induction agents. Combinations of other agents are often used to induce anesthesia or produce profound enough sedation that administration of anesthetic gases can occur. In our practice, we use ketamine and diazepam in combination in dogs to induce anesthesia, usually after preoperative sedation with very low doses of acetylpromazine. This has been a successful combination for us, reliably inducing anesthesia and still allowing us to maintain a good safety record. We have only been comfortable with this combination since we began to use isoflurane gas, though. Prior to that we sometimes had a problems with patients reacting to surgery because the ketamine/valium combination was wearing off before the anesthetic gas was fully effective. Isoflurane works quickly enough that we are comfortable using acetylpromazine and oxymorphone or other narcotic analgesic to produce deep sedation and then inducing anesthesia directly with the isoflurane gas. For cats, we use ketamine in combination with acetylpromazine, diazepam or xylazine, depending on the situation. After giving the induction agent it is still necessary to maintain the anesthesia with a gas anesthetic in most cases.

I have used three different anesthetic gases during the time I have been in practice and all are still used in some practices today. Methoxyflurane (Metofane Rx) is an older anesthetic agent that is slow to produce anesthesia and from which anesthetic recovery is also very slow. It is relatively well absorbed by the body and it is more likely to cause liver damage than other anesthetic gases. It provides more postoperative analgesic effect than the new gases, though. During the surgical procedure it is pretty hard to overdose a pet with methoxyflurane because it is hard to get it to vaporize from the liquid state in levels high enough to be immediately dangerous. For these reasons, some vets still like to use it. I do not think that these effects are sufficient to justify its use when all effects are considered, though. Halothane gas induces anesthesia faster than methoxyflurane and it is less likely to cause liver problems. It does sometimes induce cardiac arrhythmias, which can be fatal. It will vaporize in sufficient concentration to cause death so there can not be any laxity in monitoring anesthetic levels when using halothane. Isoflurane is considered to be the safest of the commonly used anesthetic gases. It is not well absorbed by the body, so it causes its effects in lower concentrations and disappears pretty rapidly once the gas is no longer being administered. Patients fall asleep quickly and wake up quickly from isoflurane. It seems much less likely to cause liver damage than the other gases and cardiac effects are less, as well. It is often necessary to use an analgesic in conjunction with isoflurane, though, since the pet may wake up so fast that there is still a good deal of surgical pain to deal with when the anesthesia is gone. Still, overall, this is the best anesthetic gas in my opinion.

There are newer anesthetic agents available now, such as propofol, which I have not attempted to use. One of the problems with anesthesia is that learning the peculiarities of a new anesthetic agent is sometimes dangerous for my patients. I know from experience that it is good to review anesthetic protocols and to consider using newer anesthetic agents at times, though. When I graduated from veterinary school barbituate induction agents were pretty much the standard in veterinary medicine. We had patients die from anesthetic procedures when using these agents but we did not seem to be losing more patients that was "expected", at least judging by conversations with other vets. It took a little while for us to give up on these agents when newer alternatives became available, especially after a disaster in which we tried a new anesthetic protocol and had two patients die in less than a month, despite a well documented study suggesting the combination was safer than our previous method of anesthetic induction. We might not have changed again except that thiamylal became hard to obtain for a period of time due to manufacturing problems. We were forced to change to the ketamine and diazepam combinations and realized that it appeared to be much safer after several months of use, although we also acquired an isoflurane anesthetic machine at about this same time. Since we have had isoflurane and stopped using barbituate induction agents we have not had an anesthetic death that I can remember. If we do start to have problems I hope we look more quickly for alternative solutions in the future.
 

Pain Relief for Pets

A number of clients have asked me if pets feel pain over the years I have been in practice. I have heard this question from people with a college degree to people who never completed high school. It strikes me as very odd that people do not realize that their pet would feel pain in most of the same circumstances that humans do. For the most part pets utilize the same nerve conductors and the same neural pathways that humans utilize to feel sensations. There is no reason to suspect that they feel pain differently than we do. Perhaps it is possible that residual psychological effects associated with pain are different in pets but even that is questionable. It is best to assume that a situation you would find painful will be painful to your pet.

There are studies that show that humans do much better post-surgically if pain is controlled well during surgery and during the time period around surgery. There are similar studies to show this effect occurs in pets, as well. Ask your vet about pain relief post-operatively. I sometimes forget to send home a pain reliever and am glad that my clients are usually willing to ask for one now.
 

Corticosteroid season

Summer is the time for itchy skin diseases. Fleas become more common, plants produce pollen, ticks are out, the humidity is high and it's hot. All of these things make dogs more likely to develop an itchy skin condition. The most effective medications for controlling itchiness in dogs are corticosteroids, probably the most misunderstood medications used in veterinary medicine.

Corticosteroids are a class of hormones produced naturally by the body and produced artificially by pharmaceutical companies. They are essential hormones. A dog's body can not function properly without them. The corticosteroids which are anti-inflammatory and used medicinally are not the "steroids" used illicitly by athletes. They are a group of medications which mimic the effects of naturally occurring cortisone. Prednisone, probably the most commonly prescribed corticosteroid, is about 4 times as potent in its anti-inflammatory effect as the cortisone produced by the body. Other cortisones available to veterinarians are as much as 25 to 30 times more potent in their anti-inflammatory effects over hydrocortisone.

Prednisone and the other corticosteroids have a really wide range of effects. This group of medications may have more actions and side-effects than any other group of medications. When someone reads the "laundry list" of effects, side effects and indirect effects of corticosteroids it is hard not to imagine that they are extremely dangerous drugs. On the other hand, when one sees the benefits produced by these medications in patients who need them, it is hard not to consider them to be truly miracle drugs. The truth lies in the middle and the trick in using these medications is to be aware of the side effects, to take steps to minimize them and to follow directions from your veterinarian very carefully. Used in a appropriate manner for their anti-inflammatory effect, corticosteroids usually can be used with a low risk of serious complications. Why do cortisones have a bad reputation? One of the reasons is that they are also used for their immunosuppressive effects, which involves higher dosages. These medications carry a medium to high risk of harmful side effects when used to suppress immune function. There is often little choice but to use corticosteroids when immune suppression is necessary, though. But that is a whole different story.

Corticosteroids are responsible for helping to maintain many ordinary bodily functions and in doing so they affect almost all cells in the body and therefore, most organs in the body. They can cause an increase in blood pressure, increased urination, increased appetite and thirst, cause mood changes, lower seizure thresholds, make changes to the relative frequency of different types of white blood cells and blood components (increasing platelets, neutrophils and red blood cells and decreasing lymphocytes and eosinophils), increase gastric acid secretion and decrease mucin production, inhibit the immune system, increase liver enzyme levels in the blood stream (and sometimes actually cause liver damage), increase the production of blood sugars, induce muscular weakness, weaken the skeletal system, decrease cartilage production and increase eye pressure or even possibly induce cataract formation, although this effect seems to be less common in dogs and cats than in humans. Pancreatitis seems to occur more frequently in pets that are given corticosteroids chronically than in those that are not on these medications.

Why would anyone want to use medications with that many possible side effects? There are no medications that come close to the cortisones for stopping pruritis (itchiness). In many cases these are the only effective medications for severe allergic reactions. They may be necessary to stop itchiness long enough to allow the skin to heal and antibiotics to control secondary bacterial infections. There is a great deal of misery associated with chronically itchy skin and the relief provided by prednisone, triamcinilone, methylprednisilone or one of the other corticosteroids is often valuable enough to make the side effects worth risking. Especially since they are less common at the lower dosages used for anti-inflammatory effects than they are at higher immunosuppressive dosages.

What can be done to avoid the use of cortisones? Treat any and every controllable source of itching. Use Frontline (TM), Frontline Topspot (TM) or Advantage (TM) to control fleas in flea allergic dogs or cats. Pets who are not allergic to fleas may be effectively treated with Program (TM) as well. I think that clipping the hair of many long haired breeds helps to reduce skin disease. Regular bathing is usually helpful but some dogs are sensitive to shampoos and most cats are hard to bathe. Rinsing with cool water is anti-inflammatory and can help to relieve itching of a "hot spot" or other small area of inflammation. Antihistamines help some dogs and cats. Currently, clemastine (Tavist D Rx) is thought to be one of the most effective antihistamines in dogs and chlorpheniramine has worked well for us in cats. Fatty acid supplementation (DermCaps TM, EFA-Z TM, others) helps other pets. Doing both helps more pets than either product alone. Vitamin E supplementation is helpful in a few dogs (we have not tried it in cats). Avoid walking your dog or letting your cat out at dawn and dusk since mosquitoes are more frequent then. Consider trial feeding of one of the newer hypoallergenic diets such as Exclude (TM) or the Purina LA or HA diets. Food allergies may be more common than we thought in the past so a two or three month trial on one of these diets is probably justified in any chronically itchy dog. Make sure that sarcoptic mange or ear mites are not present. Treat any secondary bacterial or yeast infections. Keep your pet inside with the air conditioning on as much as possible when the weather is hot.

When the above measures don't work, don't rule out corticosteroids because you have heard that they are dangerous medications. If the goal is to provide comfort for a pet, use of corticosteroids may be necessary. Follow a few simple guidelines for their use and you can help your pet be much more comfortable without too much risk of side effects.

Prednisone should be used every other day when it is used for longer than a few days. Triamcinilone (Vetalog Rx) should be used once every 72 hours since it has a longer half-life. Methylprednisilone given orally should be used every other day or every third day as well. If the injectable corticosteroids such as Vetalog (Rx) and DepoMedrol (Rx) are used it is best to use them at as long an interval between injections as is possible. Once a month or more is best. If more than 4 or 5 injections are necessary in a year it would be better to use oral prednisone on an every other day basis, if this is possible. Most veterinary specialists would suggest not using injections at all. For many practicing veterinarians this advice is impractical in every patient. Whenever possible it is probably better to use oral medications. An effort should be made to find and use the lowest effective dose that works on the every other day or every third day schedule. It is much better to give a little more medication every other day than to use cortisones daily to achieve successful itch control. If cortisones are used long term it is necessary to taper off the dose slowly when discontinuing the medication so that the pet's body starts production of cortisones before the medication is withdrawn. Pay attention to your pet and have your veterinarian recheck the skin if the skin condition seems to worsen at any time while the pet is on cortisones. Don't use corticosteroids in a dog with demodectic mange, systemic fungal infections, corneal (eye) ulcers, or in the face of undiagnosed systemic illness. If these simple guidelines are followed it is unlikely that a pet will suffer from a severe problem attributable to the use of cortisones for treating pruritis.

For clients the biggest problems with cortisones are effects that most veterinarians are not very concerned about from a health standpoint. The increased drinking and urination associated with cortisone use can be very stressful for pets and pet owners alike. If your pet is on prednisone or any other cortisone you have to compensate for the increased need to urinate by providing adequate access for your pet to appropriate areas to urinate. Increased appetite and fat retention can lead to weight gains which are hard to control. Behavioral changes can be difficult for owners and in a small number of cases aggression can occur in a pet that usually does not exhibit this type of behavior. Minimizing the dosage used and the duration of administration of cortisones will help to make these side effects less of a problem but these side effects can make it difficult or impossible to use cortisones in some situations.

Itchiness can be life threatening, too. While I can not provide validated statistics to prove this point, I am certain that more patients in my practice have died from secondary bacterial infections that occurred due to a itchiness than from harmful effects of cortisones. We treat several pets a year in which the wounds from itchiness have led to skin sores attractive to flies which led to maggot infestations. Some of these pets die. Many pets are euthanized because their owners can not tolerate the constant scratching, smelliness from secondary skin infections and ear infections. I have had more than one conversation with a pet owner requesting euthanasia who refused to use corticosteroids because they were dangerous. I am not sure how anything can be more dangerous to a pet than euthanasia and these conversations always mystify me. When the itchiness reaches a life-threatening level why not use a medication to control it, even if it does have some negative side effects?

Is the comfort provided by cortisones worth the risk of side effects? In many cases the answer is yes. If your pet is miserable during the summer from sustained itchiness and other treatment measures aren't working don't rule out cortisones. In most cases it is possible to regain control of a skin condition and use cortisones for relatively brief periods of time. Even in pets where short term use isn't possible careful long term use is usually well tolerated by pets. Use alternatives if you can but don't get so hung up in the hype surrounding cortisones that you find yourself considering euthanasia more reasonable than cortisone use.
 

Quick Tips for Summer Travel with Pets

Pets traveling interstate on airlines are supposed to be accompanied by a veterinary health certificate. In practice, airlines rarely ask for this document, but it is better to have it and not need it than to need it and not have it. International travelers usually need a health certificate specifically for the country they are heading for. This can take some time to acquire or there may be regulations concerning timing of vaccinations that must be met. When taking a pet on international trips you have to plan well in advance to meet import requirements.

If your pet must fly do not sedate it for the trip without very good reason. The combination of lower atmospheric pressure in the cargo hold and the sedative can have fatal consequences.

Pets are at sometimes at the greatest risk of problems when on the ground at the airport. Make sure you are there to pick your pet up promptly so that it is not left in a hot baggage area for a long period of time. Get your pet before you get in a long rental car line, for instance.

Remember that you will not be able to stop and leave a pet in the car in hot weather. Plan your trip accordingly. Make sure that any motels or hotels you plan on stopping at accept pets.

Cats should probably be confined in some manner in the car on family trips. It is very very hard to catch a cat that gets frightened and runs away from a car at a rest stop. We have had several clients lose cats in this manner and it is really heartbreaking when it happens on a trip and there isn't enough time to find the cat. Take a carrier with you and keep your cat in it whenever the car doors are going to be opened.

It is a good idea to ask your vet for a copy of medical records if you have a pet that has a chronic problem or if a pet has been ill recently. Take medications with you, including heartworm medications and other periodic medications that might come due for administration while you are traveling. Veterinarians are prohibited by law from dispensing many medications unless they have examined a pet and established a doctor/patient/client relationship, so it can be a hassle to get medications you have forgotten.

Remember that you have to plan on traveling slower when you are traveling with pets, so allow time for this.

Write down your veterinarian's name, address and phone number somewhere you can find it readily. We practice in an area with a lot of visitors and it is very frustrating to need a medical history or help identifying a medication a pet is on and discovering that the client can not remember the name of the veterinary hospital. Sometimes clients think they remember their vet's name -- but there is not vet with that name that directory assistance can come up with.

If your pet is on a special diet or sensitive to changes in food, take extra food with you, too. It can be hard to find a particular dog food in a different town sometimes.

Some pets do better if you don't take them with you. A good pet-sitting service can be just the right thing for a cat that is nervous anywhere but its own house or a dog that is used to being home by itself part of the day. Most dogs adapt readily to being boarded, usually better than people think they will. If you are traveling in hot weather in a car there is a very good chance your pet will enjoy the week or two in the kennel a lot more than in the car.

As you travel to new places try to anticipate the problems your pet might experience. A hiking trip in the West means watching out for foxtails -- grass awns that can cause nasty wounds. Letting your dog run on the beach here on the Chesapeake Bay means that oyster shell cuts may be a problem. If you are traveling to an area with Lyme disease, take precautions to avoid ticks. If you are traveling to an area with heartworms and your dog is not on preventative medications, ask your vet to supply you with enough for the period of the trip and two months afterwards, too. If you are not sure of the possible problems you might encounter on a trip try to talk to someone in the area or call a veterinary hospital where you are going and ask for a advice about local problems.

It is possible to have a great vacation that includes your pet but the secret is usually in the planning. Do a good job of that and your trip will probably be safe and enjoyable, too.

As always, we sincerely appreciate your support of the VetInfo Digest and the VetInfo Web Site. It is much easier to provide these services with your help.

Thanks!
Copyright, TierCom, Inc., 1998
Tiercom, Inc.
P.O. Box 476
Cobbs Creek, VA 23035
The opinions expressed in this newsletter are solely those of the author, Michael Richards, DVM, unless otherwise noted in the text. Michal Justis is our web designer and graphic artist.