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VetInfo Digest August 2006

Table of Contents:

Seizures in Dogs and Cats, continued

Evaluating Veterinary Information

Slocum TPLO Plates Causing Problems

This Month's Note:

Ten years ago this month Michal and I started to put together the web site that we would eventually call vetinfo.com. We hoped to provide a place where pet owners could find reliable information about health care issues affecting their pets. We didn' really expect to become the local computer "" in the process but each of us has learned some aspect of dealing with computers that has made our friends and neighbors seek our help in handling computer related problems. Last month, despite all of our accumulated knowledge we made one of the most basic mistakes. Not to excuse this too much, but it is important to the story that you know that both Michal and I live in rural areas where there is no easy and affordable broadband access. So we upload and download the web pages, mail, virus signatures and handle all the other online tasks that accompany producing a web site over dial-up connections. Which means that it takes hours to back up our web site and usually these have to be hours in which we are paying attention because dial-up ftp connections frequently fail during long downloads and uploads. So when our rented server, a state away from our homes, went belly up last month, we didn' have a recent back up of the site. Of course, the first thing that occurred to me was a line I wrote a few months ago - " you don' back up your data, you will lose it." Fortunately, we didn' lose too much. But it is a lesson to keep in mind!

Seizures and Seizure Control, continued from June and July:

There are several medications being used in human medicine that have shown promise in treating seizures in dogs. There is less information available on newer treatments for seizures in cats, probably due at least in part to the fact that seizures are less of a problem for cats and cat owners. There are also several medications that are used to treat seizures in people that have been explored as possible seizure control medications for pets without much success. Since it may be tempting to think that any new seizure control medication may have advantages I' provide a list of the ones that appear to be less promising, as well.

The most promising of the newer medications for dogs appear to be levetiracetam (Keppra Rx) and zonisamide (Zonegran Rx). Both of these medications have benefited some dogs when used alone or in combination with other seizure control medication in small studies. Gabapentin (Neurontin Rx) has also shown some promise, mostly for treatment of partial seizures.

Zonisamide can be given twice daily with a recommended starting dose of 2 to 4mg/kg. It is probably too expensive for most people to use for treatment of epilepsy in large breed dogs but it has been used as a primary treatment or secondary treatment in small breed dogs. It is reported to produce side effects similar to phenobarbital and potassium bromide but somewhat less pronounced. There has been one well documented study of zonisamide use in dogs (Dewey, 2005) and in that study 58% of the dogs experienced seizure control similar to phenobarbital and 42% appeared to have an increase in seizure events compared to their pre-treatment state. This is definitely a mixed result but zonisamide still should be considered as an adjunct therapy for dogs who do not respond to the more traditional seizure control medications adequately. I am not aware of any studies or case reports of zonisamide use in cats.

Levetiracetam is thought to be the seizure control medication with the least potential for side effects in humans. This makes it an attractive medication for use in dogs and cats, on the presumption this would also hold true for these species. In humans the incidence of side effects associated with levetiracetam is supposed to be very close to that of a placebo drug. It would be very nice to have a seizure control medication with so few side effects. However, at the present time I am not aware of a firmly established dosage or monitoring method for this medication. Despite this, it has been used in both dogs and cats with some success. The dose range for dogs is estimated to be 5 to 25mg/kg every 8 to 12 hours (Platt) and for cats to be 10 to 20mg/kg every 12 hours (Rusbridge). This is also an expensive medication compared to phenobarbital and potassium bromide but its use in small dogs and cats is probably affordable for many pet owners. It can be used in combination with other seizure control medications if necessary. Dr. Rusbridge recommends combining it with propentofylline (Vivitonin Rx) or phenobarbital for cats with seizures that are difficult to control with one medication alone.

Gabapentin appears to work well in conjunction with Phenobarbital to control refractory seizure activity in some dogs. The published protocol for gabapentin is 35 to 50mg/kg per day, divided into two or three doses over the course of the day. It is thought to work better for control of partial seizure activity than for generalized seizures but it shows promise in treating refractory seizures when used in combination with phenobarbital or potassium bromide (Govendir 2005). This too is an expensive medication which may make it cost prohibitive for use in large dogs but perhaps not for smaller dogs. I am not aware of studies involving the use of gabapentin for seizure control in cats but in case reports an initial dosage of 10 to 40mg/kg every 8 hours has been recommended. Gabapentin has been studied for use in pain control in cats and it appears to be reasonably safe to use in those studies. Hopefully this is also true for its use in seizure control.

Phenytoin (Dilantin Rx) has almost no use in dogs because the half-life of the drug is so short in dogs that it needs to be given every two to four hours to be useful. Consequently, phenytoin isn' used much in veterinary medicine. There may be a use for it in cats experiencing seizures that are not responsive to other medications, though. Unlike dogs, the half-life of phenytoin in cats is reported to be about 40 hours, making it possible to use this medication in cats on a once daily basis for seizure control. Unfortunately, the long half life also makes it very easy to overdose cats with phenytoin and so it is necessary to monitor serum levels of the medication on a regular basis to try to avoid this complication. Phenytoin is administered at a dosage of 1 to 5mg/kg per day. There is a phenytoin elixir, making dosing reasonably easy. Due to the potential to slow metabolization of phenytoin by administering other medications it is recommended that phenytoin only be used as a single agent for seizure control in cats. Despite the possible advantages of once daily dosing for many pet owners, phenytoin has not become a standard medication for seizure control in cats due to the relatively high potential for toxicity unless it is monitored very carefully.

There are a number of other seizure control medications used in humans that are tempting to try in dogs and cats. Of these, valproate (Depekene Rx, valproic acid), clorazepate (Tranxene Rx), gamma-vinyl-gamma aminobutyric acid (Vigabatrin Rx), carbamazepine (Tegretol Rx), oxycarepine (Trileptal Rx), clonazepan (Lamictal Rx) and lorazepam (Ativan Rx) all have problems with side effects, rapidly decreasing effect, or short half life of the medication which limit the use of the medication in dogs and cats.

Due to the potential for side effects and toxic reactions to most of the seizure control medications there is a strong interest in alternative approaches to seizure control, through medication sources such as homeopathy and herbalism, as well as through different ways to avoid seizures such as "" diets, aromatherapy and dietary supplements. It is likely that some dogs or cats respond to some of these alternatives but to the best of my knowledge the only food supplement that has shown any promise is taurine (van Gelder 1977, Eppler 1999), which seems to help control seizure activity in some cats. Taurine is supplemented in most cat foods at the present time and it is hard to say if additional supplementation would be helpful or not. I can not provide much information on herbal therapies for pets except to note that there are no strong recommendations from veterinarians practicing herbal medicine except for those using traditional Chinese herbal therapies and the recommendations from these practitioners seem to encompass a wide enough variety of herbal variations that it appears that experimentation with a number of treatments until one seems to benefit the pet is the general approach to therapy.

Hypoallergenic diets are sort of a misnomer, in most cases. There actually are three diets specifically manufactured to produce proteins that are unlikely to cause allergies. These are z/d ™ from Hills, and LA™ and HA ™ diets from Purina. Most of the people referring to hypoallergenic diets are not actually referring to these products, though. They are referring to diets which contain a protein source the pet is not allergic to. How is this determined? Primarily by making an effort to choose a protein source that the pet has never been exposed to previously. There are lots of diets with odd protein sources, like alligator, ostrich and duck, which help to ensure that the pet is eating a protein source it has not been exposed to previously. The trick is making sure that these diets and only these diets are fed during the trial period. If seizure activity drops off dramatically, diet may be an influencing factor in the seizure activity.

When using any seizure control medication, or any other approach to seizure control it is really important to understand that the only really good way to evaluate success or failure of the therapy is to keep careful records of seizure activity. Seizures are so widely variable in how frequently they occur and how severe they are that it is easy to be fooled into thinking a medication or treatment is responsible for lulls in seizure activity or to assume that seizure activity has lessened when in fact it has not. Keeping a careful log of seizure activity can help you to determine if the treatment methods are helping.

One other approach to seizure control that can be beneficial is trying to avoid situations or conditions that have been associated with seizure activity in the past. If you are keeping a log of seizure activity it is easier to recognize these conditions.

Most seizures in dogs and cats appear to occur during periods of rest but not necessarily sleep. Owners often miss this connection because the period of rest may occur after a period of really frenzied activity or stress and it is easier to recognize that as a potential problem than the inactivity that follows. A fairly classic example of this is a pet who seizures consistently after being boarded or when left home with a pet sitter and then reunited with the family. The major change in the pet owner' mind is the fact that they left the pet at the kennel. The pet owner sees a really big response when the pet is greeted and brought home. The pet may be very active for a few minutes at home. The seizure tends to occur, though, after the pet becomes content that it is home and relaxes. What is probably happening with the pet is a response to being tired over a long period of time due to the noise, activity and stress of the kennel. This overstimulation of the nervous system has prevented seizure activity because it couldn' reach the trigger threshold with the increased brain activity. Once the pet relaxes enough to slow brain activity down there is an opportunity for the seizure stimulus to control enough of the brain activity to lead to a seizure.

Keeping situations in which the pet feels compelled to stay awake or is severely stressed to a minimum can limit seizure activity. This can be hard to manage when it is necessary to board a pet but for pets with seizures activity it may make sense to try a pet sitter instead of a boarding kennel so that the pet can stay at home. When playing with really hyperactive pets it is helpful to stop before they are really tired or obviously overstimulated. I have heard of several cats who have seizures after intense laser pointer play, apparently because they get so into this activity that they are both very tired and very overstimulated when it stops. When activities that have been associated with seizure activity in the past can' be avoided it is at least helpful to know that a seizure is likely and to make the pet as safe as possible when the seizure occurs.

Keeping pets safe during seizures is something that can take a little bit of forethought and effort. Subscriber Sandy Schneider sent a list of things that she does to help prevent her cat, Baby, from injuring himself during seizure episodes. These include blocking off open railings on upper floors, preventing access to stairs, balconies and other dangerous spots when a pet can' be supervised and being aware of the risks of swimming pools, space heaters and other dangers. It is very useful to think about the safety of your home for a pet who seizures, especially pets who are slow to recover full consciousness after seizure activity. In our practice we have had a Labrador retriever who suffered from seizure activity drown during a seizure. It is also helpful to ensure that all family members are aware of these risks and make an effort to protect a pet during seizure activity. There still seems to be a persistent fear that a pet might " its tongue" during seizure activity but if this actually happens it has not happened in our practice in over twenty-five years of practice, at least to the best of my knowledge. Don' get bitten by a seizuring pet by trying to put something in its mouth during a seizure to protect its tongue or lips. If injuries occur they can be dealt with after the seizure activity is over.

While seizure activity seems to be extremely upsetting for most of my clients the first time they witness it, most pet owners learn to accept seizures as a part of their pet' life over time. For the most part seizures seem to be very similar in a particular pet each time they occur and the pattern becomes familiar and easier to accept. If medications for seizures are necessary they usually work and seizure activity becomes less frequent over time. Most pets are not especially bothered by seizure activity and many pets really appear to be unaware a seizure occurred. This is a condition that you can live with and that can be controlled well enough that your pet can continue to have a good life despite occasionally seizure activity.

Evaluating Information Pertaining to Pet Health

There are a number of sources of information that pet owners rely on. Determining which information to trust can be a difficult task, though. This is one of the areas in which many veterinarians have an advantage over pet owners. Most veterinarians are taught to rely on information that has been scientifically validated first. I would say exclusively but that isn' even possible, much less practical, with the current state of veterinary information. Veterinarians are also taught how to recognize scientifically valid information and they usually acquire some skill at recognizing information likely to be valid even though it can' yet be proven scientifically. The set of skills necessary to do this are not that difficult to explain but it may take some effort to try to acquire them. It is a worthwhile task if you really value understanding health care information as it applies to your pets and even to yourself, though.

When veterinarians first encounter new information I think that the first thing most of them do is make an initial judgment about the source of the information. If I hear that there is a new form of parvovirus from a client who heard it on TV very recently, I would be interested enough to pursue more information. It is feasible that this could occur and the original source has some obligation for accuracy, even if it is limited. When a client came in and requested that I not touch the bangs on his Briard' forehead when I shaved around a tumor close by that I was planning on removing, because " you cut the hair around a Briard' eyes he will go blind," I simply asked where the information came from. When he told me that the breeder told him that, I tended to discount the information. It seemed extremely unlikely to be true and the source was questionable for this type of information. Breeders can be an invaluable source of information for specific breed problems but they are also really terrible about spreading incorrect information indiscriminantly. I did look into this prior to prepping for the surgery, anyway, since the consequences of completely discounting the information if it was true would be pretty severe. There is no evidence at all that it was true. I suspect that somewhere a veterinarian clipped a Briard' hair over its eyes, revealing a pre-existing eye problem which was subsequently blamed on the vet (or perhaps the groomer).

If the Briard' owner had claimed that he heard the information about cutting the hair over the eyes leading to blindness from his previous veterinarian, I think that I would also have dismissed it as unlikely. I hate to say this, but veterinarians are often a source of bad information, as well. While I doubt that many vets would be fooled by information suggesting that cutting hair could lead to blindness anywhere other than very high altitudes where the sunscreen value of the hair might matter, I know for a fact that veterinarians sometimes pass on information that is simply wrong.

The most likely scenario in which you receive bad information from your vet is when you ask a question about something that is not a routine part of practice when the vet practice is extremely busy. It is extremely tempting to answer off the wall questions during a busy exam with an "" guess rather than taking the time to dig out the textbooks, review the literature and provide an answer backed up by scientifically valid studies. This also happens with phone inquiries. If you call and ask a question, such as " it bad for a dog to take two blood pressure pills meant for me?" and the receptionist puts you on hold, then comes back in a minute or two and says, " says it should be OK," you should be suspicious that you are only getting your vet' best guess.

If you ask your vet a complex question during a regular office visit it is also very likely that you will get a summation of the vet' current knowledge, which may or may not be great, about the topic you picked. There are lots of times when this is likely to happen but just to give you one example, I have had a client ask me, " you think that my dog might be progesterone deficient since she lost that last litter?" right at the end of a normal visit when I knew someone else was waiting their turn. I can pretty much guarantee you that only a small percentage of veterinarians can answer this question without taking some time to research the answer. This isn' a topic that comes up during a regular day at the office very often and the available information is contradictory. It took me two or three hours of research to feel comfortable answering the question. If you need very specific information about complex or unusual problems make sure that you give your vet an opportunity to do a little reading before answering your question. A good way to do this is call and leave a message with the receptionist. If my client had called the office and said " need to know about progresterone levels and how they affect pregnancy, can Dr. Richards call me back to discuss that?" I would have made an effort to be prepared to provide an answer when I called back. Alternatively, if she had mentioned to the receptionist that she was concerned about this prior to the office visit I would also have made some effort to be better prepared.

The tendency to come up with a best guess is particularly worrisome when clients call with questions about possible poisonings, nutritional needs, potential drug reactions and seeking information about newly reported diseases or disorders and insist on talking to the vet immediately. Clients seem to assume that veterinarians should know this type of information without having to look it up. I may not be typical of most veterinarians but only rarely is it possible for me to answer questions like this immediately when asked during a visit or phone call. This is one of the reasons that I don' do phone consultations. It is just too tempting to appease the person on the other end by providing a good guess instead of a researched answer. If you want a really good answer to a difficult question, you have to give your vet time to look into the question before providing an answer. Doing that takes more time than can usually be allotted to a phone call or office visit. It is definitely reasonable to ask your vet to look into something and get back with you, though.

When they think about it, most veterinary clients probably know that their relatives and friends are not always a good source of information. Most probably even realize that taking medical advice from their dog' groomer or breeder carries a bigger risk of getting incorrect information than getting medical information from their vet. There are a few areas in which groomers and breeders seem to be particularly poor information sources. Very few breeders appear to understand vaccination protocols or the real risks and benefits associated with the use of vaccinations. Be very careful following advice from a breeder over that of your vet. In many cases specific nutritional advice from breeders and groomers tends to be questionable in quality, as well. While veterinarians are probably under trained in nutrition, they still have some training. Most breeders and groomers do not. Finally, your vet is a better source of information on flea control than most groomers and breeders.

If you decide that you need to research your pet' health needs on your own because you aren' getting enough information from your vet and other contacts, how do you decide which information to believe as you search the internet, textbooks, magazines and other sources of information?

Veterinarians have a distinct advantage when it comes to searching for literature references. We have access to a number of journals, continuing education meetings and other ways to become familiar with certain researchers, institutions and journals over time. After awhile it becomes apparent which of these are good sources of information for various problems. In some cases one researcher may be the best source of information for one disorder in a field and another researcher may be better at another. When conflicts occur in the published information, veterinarians at least have some idea of who has been a reliable source of information in the past. This is one reason that working with your vet to research information can be much better than trying to do it on your own.

While it is often important to veterinarians who wrote a journal reference, it is hard for veterinary clients to discern much by the author' name, in most cases. There are other hints about the validity of information in a journal reference, though. In most cases in which an author works for a company or receives major funding from a company, there will a note which acknowledges that fact.

It is usually a good idea to be suspicious of information that comes directly from a drug company, equipment manufacturer or other source who has a vested interest in the outcome of the research described. If there is no collaboration for information from a source that clearly has an interest in influencing you to use their product or services, it can be very difficult to decide whether to trust the information enough to act on it.

Most people can look at a study, if they try, and determine whether it is an appropriate approach to the problem. For example, if you are looking for a good flea control product and you find a study that shows 100% kill of adult fleas it starts out looking very good. If you read further and find that the effectiveness of the product was studied after 30 minutes and never longer than that, you might be a little suspicious of it. On the other hand, if there is data to show a duration of action of a month or so, then you might think it was more practical for your purposes. The duration of a study can have a major impact on the usefulness of the information. This was a major problem with vaccine studies for a very long time. Duration of action for vaccinations was studied for one year and no longer. There was no way to determine how long the vaccine actually provided protection because it was never studied. Fortunately, longer term studies are now available.

Lots of people are uncomfortable with statistics but usually you can still get some idea of whether a study really meant much by reading them. To give you one example that I really consider a classic case of misusing data, there was a study done which was a five year follow-up on dogs who had cruciate ligament injuries which were either repaired with a surgery referred to as an " the top" surgery, repaired with surgery referred to as extracapsular stabilization or not repaired at all. After five years it was not possible to distinguish between any of the three groups in terms of arthritis formation or disability associated with the original injury. The author' conclusions were that there was no significant difference between over-the-top surgery and extracapsular stabilization. I have always felt that the correct conclusion, since the dogs who weren' operated on were doing just as well, was that neither surgery did much for the dogs over the long run. It was there in the data, the authors just ignored it. Take the time to read the statistics and look at the conclusions when evaluating a study.

With the advent of the internet it is possible to find summaries of a wide number of articles on various subjects in veterinary medicine. Remember that often you are looking at a condensed version of the actual study. You can get a good idea of the general outcome but summaries are often the author' opinion of what was important or the author' attempt to make you read the whole study. I doubt there are any veterinarians who have access to every journal included in online databases so there may be no convenient way to read the whole study. Keep in mind that while summaries of journal references are useful, they are much less useful than the full text of the reference. It is hard to judge data that just isn' there to look at due to the way the summation of the article was done.

Some of my clients have caught on to the fact that a lot of medical studies involve very small study groups. While it may be statistically valid to draw conclusions about the general population of dogs from relatively small studies, I think that most veterinarians and most people realized that a study involving ten patients has more potential for misleading information to occur than a study involving thousands of patients. Check out the size of the study population whenever possible.

Most of our clients also recognize that a study that includes a control group, which is not subject to the study' effects, is also a necessary condition for a study to be considered truly valid.

When control groups are not used, or not used properly, it is important to consider this when drawing conclusions from a study. Information from a study done without controls is simply less reliable overall than information from a study that does have a control group.

Textbooks tend to be a good source of mainstream information pertaining to problems covered in the text. On the whole, textbooks reflect the current state of information a few months to a year or so prior to publication of the book. While they may not contain up to the minute facts, editors of texts generally require that the information contained in them have at least some validity. Your vet can often tell you the best text to get information from concerning a specific topic.

When you hear something about your pet' health that intrigues you, think about where the information came from. If it came from a source such as a relative or friend ask where they saw it and try to track down that source. If it came from the TV, the newspaper or a magazine, look for information that can lead you to the original reference source. Track down the source for yourself and take the time to evaluate the information if it is of great importance to you. Only when you can identify the original source, consider realistically if that source is likely to be valid, examine how any studies were done and whether the author' conclusions seem to match the data in the study can you really begin to trust the information.

Double check on information that you get from your vet, your groomer or your pet' breeder. Even if the information seems to make sense check into it if major decisions must be made based on the information, unless the situation is an emergency. It would be great if vets were always fully informed when they answered questions but there probably wouldn' be any time to get real work done if they were!

It is worth taking the time to make sure that information about your pet' health needs is valid prior to acting on it.

Problems with Slocum TPLO Plates

In the July 2006 issue of the American Journal of Veterinary Research (Boudrieau, et al), there is a report of problems with bone infection and bone cancer associated with the use of TPLO plates made by one manufacturer, Slocum. If you dog had surgery to stabilize a knee (stifle) after cranial cruciate ligament rupture using the TPLO technique it would be a really good idea to ask your vet if the steel plates used in the repair came from Slocum. If so, you may want to consider having them removed. There are several manufacturers of these bone plates and at the current time only the Slocum plates have been confirmed to have a role in the problems of bone infection and bone cancer that occurred after surgery in a small number of dogs.

Thanks for your Support!

VetInfo Digest

P.O. Box 476

Cobbs Creek VA 23035

All opinions in this newsletter are those of the author, Michael Richards, DVM