VetInfo Digest

August 2007

 

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Table of Contents:

 

New Medications

 

New Uses for Old Medications

 

Microchipping

 

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This Month’s Note:

 

Moe and I are going on a real vacation for the first time in several years this August. I do not intend to take a computer with me, so there will be a break in answering questions from August 14th until Sept 1st .   It is likely that the September VetInfo will be late, as well.  It is hard to leave a small practice like ours because relief veterinarians who are willing to take on the responsibility of running a small practice are hard to find. Every now and then, though, it just becomes necessary to take a break.

 

Some of my clients become quite upset when they have to come to the practice and find that we aren’t there. I try to tell them that we’ll be around longer and that we’ll be able to function better with less chance of burnout if we take a little time off but the message doesn’t seem to sink in.  Try to be kind to your vet when you miss him or her due to time off for vacations, continuing education or other concerns.  I can guarantee your effort to do that will be appreciated.

 

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New Medications

 

There have been a number of new medications, vaccinations and flea treatments approved for use in pets this year. It is possible that one of these medications may be helpful for your pets.

 

Pimobendan, a drug that has been used to treat congestive heart failure (CHF) and cardiomyopathy in dogs in Europe for several years was recently approved for use in the United States.  It will be marketed under the brand name Vetmedin.  It is only approved for use in dogs at this time. This medication is meant to be used in addition to the current medications available for use in CHF, not as a replacement or alternative for the other medications. It works by causing dilation of blood vessels, which allows the heart to pump more easily and by increasing the contractility of heart muscles. 

 

Chronic heart failure is a common problem in older dogs. It is less common in cats. In both species the primary medications for treatment of symptoms associated with heart failure have been diuretics, particularly furosemide. There is clear evidence that diuretics play an important role in patient comfort and in increasing longevity in patients who have CHF.  Diuretics are the preferred starting therapy for CHF and pimobendan should not be used as a substitute for diuretics. It is acceptable to use pimobendan and diuretics at the same time.

 

Over the last few years it has also been increasingly common for angiotensin-converting enzyme inhibitors (ACE inhibitors) to be used in conjunction with diuretics to aid in the treatment of chronic heart failure. These medications also have a good track record at this time but are not effective enough to use alone, without diuretics, for most patients. It is acceptable to use ACE inhibitors, diuretics and pimobendan at the same time.

 

In studies in humans there were more complications when patients were on digoxin when pimobendan was added. This has not been studied in dogs, to the best of my knowledge. If your dog is currently on digoxin you may wish to be a cautious about adding pimobendan.

 

Pimobendan is classified as a inodilator because it has inotrophic effects (increasing the strength of the heart muscles) as well as vasodilator effects, which make it easier for the heart to pump blood. It is meant to be used in conjunction with the medications listed above, not as a substitute for them.  It may be more helpful in cardiomyopathy than in congestive heart failure, at least for Doberman pinschers. Results in cocker spaniels, with a slightly different type of cardiomyopathy, were not as good.

 

In humans at least one study found that patients on pimobendan fared worse than patients not on the drug. There is no direct correlation between human and animal studies so it is possible that even if this study holds true in people it won’t be true for dogs. In addition, other studies showed a lower risk of death in patients on pimobendan.  However, it is reasonable to be cautious about adding pimobendan to your dog’s medications for chronic heart failure at this time, especially if everything seems OK without it. As it is used more it will become more clear whether and when it is beneficial to patients with differing types of heart disease.

 

 

Promeris ™

 

I have mentioned Promeris in a couple of the previous VetInfo issues so I thought I should make it clear that I don’t have any connection with Fort Dodge Laboratories.  It is just that it has been a while since there was a new flea and tick control product. This, combined with the growing suspicion among veterinarians that resistance may be developing to Frontline ™  brand products, makes Promeris news.  

 

For cats the sole ingredient in Promeris is metaflumizone.  The dog product, Promeris Duo ™, which should be available early this fall, contains metaflumizone and amitraz.  It is anticipated that metaflumizone alone should be very safe as the toxic dose for mammals is far higher than the dose need to kill fleas.  Amitraz has been FDA approved as a sole ingredient for treatment of demodectic mange and in a tick control product for some time.  Amitraz does not have the safety margin that metaflumizone seems to at this time but the dose and application method appear to make it safer to use topically for tick control than as a demodectic mange treatment.  Time will tell if this is the case but if you are having problems with fleas and ticks and feel that your current treatment needs to be changed, it is reasonable to try Promeris Duo based on preliminary test results.

 

It is anticipated that this product will work very well for flea control and tick control, in dogs, based on the data presented to date. It has a residual effect that exceeds one month duration, although the product is designed to be used once monthly.

 

In the southern portions of the U.S., where flea control can be quite difficult, it is always good to have another choice in flea control medications. It may be helpful in preventing resistance to Promeris if it is used in rotation with one or two of the other good quality flea control products, Frontline, Advantage ™ or Revolution ™.

 

Advantage Multi ™

 

Advantage Multi is a combination product from Bayer ™ that consists of imidocloprid, the primary ingredient in Advantage ™ and moxidectin, a heartworm prevention medication that was last approved in injectable form under the brand name ProHeart ™.  It is anticipated that the problems which led to the recall of ProHeart will be avoided by the topical application.

 

Advantage Multi prevents heartworm disease and controls fleas and intestinal worms.  It is nice to have a combination product, especially for cats, for these problems. However, the only other topical flea control product, Revolution ™, has a lower than expected prevention rate for heartworm disease. It only prevents the disease in about 90% of patients, which isn’t good enough. It remains to be seen whether this is a problem with the application method or the medications used. If it is the application method, there is a chance that there will be similar problems with Advantage Multi, since it is a topically applied product.

 

I am reluctant to try Advantage Multi at this time for my patients due to the worry over whether topical application could lead to problems with heartworm prevention but I guess that this could be a good product for dogs who just won’t take pills.

 

Cerenia ™

 

Cerenia ™  ( maropitant citrate) , from Pfizer ™, is a new product for controlling vomiting in dogs. It is approved in an injectable form and in pill form. The injectable form could prove to be a very important product for use in puppies with parvovirus and in conjunction with chemotherapy to limit vomiting due to the chemotherapeutic medications. The oral tablets are approved for use for car sickness in dogs. While it probably won’t help with the nervousness and drooling associated with fear in dogs who just don’t like cars, it will be nice to have a product that can at least control vomiting in dogs prone to that during car rides. At the present time there is not an approved cat product and I have not yet seen any advice concerning the use of this product in cats.

 

Ft. Dodge CaliciVax ™

 

A new strain of calicivirus has occurred in shelters and a few veterinary practices across the United States. This strain has resulted in a very high death rate in affected cats, with many dying within 24 to 48 hours of the onset of disease signs. This strain of calicvirus is being called virulent systemic feline calicivirus  (VS-FCV). 

 

Cats affected with VS-FCV have clinical signs that can include very high fevers, swelling of the face and/or legs, ulceration of the skin, especially on the face and death in a high percentage of cases.

 

The strains of calicivirus found in most vaccinations will not protect against the virulent systemic strain. CaliciVax is the first vaccine approved for use against this strain. It also cross protects against a number of other strains of calicivirus.  Ft. Dodge claims that this vaccine protects against a number of strains of calicivirus that traditional vaccines will not provide protection for.

 

It is not likely an individual cat or even a small group of cats living in a household would be exposed to VS-FCV.  However, there may be some benefit to getting protection against the additional strains of calcivirus.  On the other hand, this vaccine is a killed vaccine, which means that it may not provide protection until a second dose is administered and may be more likely to produce vaccine associated sarcoma  (Ft. Dodge representatives dispute this).

 

The origin of the VS-FCV strains is hard to determine. At the present time the working theory seems to be that they are mutations of ordinary calicivirus. If so, then the mutations are arising independently of each other and there is a chance that the vaccine will only work against a limited number of possible strains, according to the U.C. Davis shelter medicine web site.  This is a very good web site for those of you who have an interest in shelter medicine. The URL is:

 

http://www.sheltermedicine.com

 

With all of this in mind, it is still unclear whether or not it is better to use the VS-FCV version of CaliciVax.  We have not made the switch to this vaccine in our practice as I still prefer modified live vaccination to the use of killed vaccines in cats at the present time and because we think the risk of the disease for cats who are living in pet homes is very low.  If you feel that your cats may be exposed because you foster kittens for the local animal shelter, attend cat shows or are exposed to large numbers of cats in some other way, it seems reasonably safe to use the vaccine.

 

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New uses for Old Medications

 

Gabapentin  (Neurontin Rx) and buprenorphine

 

Gabapentin is not a new medication and it is not approved for use in dogs or cats. Despite this, it is gaining popularity as a pain relief medication in pets, especially cats. There are few choices for relief of chronic pain in cats so any medication that might provide some benefits gets a lot of attention.

 

The International Veterinary Academy of Pain Management has a web site  (http://www.cvmbs.colostate.edu/ivapm/ )  that provides pain relief advice for veterinarians and pet owners. According to information on this site, gabapentin can be used in cats at a dosage 25 to 50mg per cat initially (approximately 5 to 10mg/kg), given every 8 to 12 hours. If necessary the dosage may be increased to 100mg every 12 hours. 

 

If your cat has chronic pain and it has not been possible to find a safe and effective pain relief medication you may want to consider the use of gabapentin.  If your veterinarian is reluctant to try a new medication without more information give him or her the web link. There is a section for veterinary professionals on the site.

 

If you check out this site there is also mention of the use of buprenorphine for pain relief in cats. We have been using this for some time to control pain associated with surgery and last year we decided to try it for some of our arthritic patients. It seems to provide reasonably good relief from arthritis pain for our patients. We use the injectable version of the medication but give it orally, which seems to work fine. We use the standard dosing schedule (0.03mg/kg) but only give it once a day when using it chronically.

 

Dextromethorphan

 

Many of you are familiar with dextromethorphan as an ingredient in cough syrup.  We sometimes use dextromethorphan to control coughing in pets. Recently there has been a suggestion, not well documented, that dextromethorphan may be beneficial for use in dogs who suffer from atopy and are not well controlled by corticosteroids. The working theory is that some dogs have both a behavioral and medical reaction to atopy and that some of the self-destructive itching is due to behavioral responses to the itchiness.

 

Dextromethophan has been advocated for use in controlling this aspect of atopy. I can not attest to how well it works clinically as this is new information for me, too. However, we have not had significant problems with side effects or adverse reactions to dextromethorphan, with the exception of a few pets that seem to get very sleepy when it is used, so we feel that it would be safe to try it.  The recommended dosage is 2mg/kg every 12 hours. Dextromethorphan is available in tablet form for pets. It is usually easier to give tablets than to try to give OTC cough medications in liquid form. 

 

It is best to try to consider whether or not there is a component of the itchiness that seems to be worsened by anxiety or behavior that suggests that the pet has learned to have an exaggerated response to itchiness before using dextromethorphan.  Atopy can be very frustrating to treat so having an additional option is nice, even if it helps only a small number of dogs.

 

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Microchip Controversy

 

Most of my clients think of microchipping their pet as a simple decision. They decide whether or not they think there is much risk of their pet getting lost and then whether or not it is worthwhile to pay the cost of microchipping and registering their pet based on that risk.  We do not have a high demand for implanting microchips as many of our clients appear to have decided that for their pets the risk of loss is low.  The clients who do make the choice to have a microchip implanted seem happy with their decision most of the time, though. 

 

It is likely that many pet owners would be surprised by the actual risk of a pet getting lost or stolen. It is estimated that approximately 1 million of the 75 million dogs in the U.S. are reported lost or stolen each year. An individual dog has a 1 in 3 chance of being lost at least once in its lifetime. The recovery rate for pets that have no form of identification at all is quite low.  Simply having a collar on with identification tags increases the chances of recovery dramatically.  Having a microchip implanted increases the odds that a pet will be recovered even more, if the pet owner has taken the time to register the pet in a database. This is a step that is missed as much as 40% of the time when vets implant microchips and rely on the owner to send in registration information.  If the shelter finds a microchip is present but the owner can’t be identified through chip registration it is likely they would hold off longer than usual on euthanasia but it is still much better to register the chip with one of the databases.

 

There are small risks associated with the use of microchips. There has been at least one well documented case of a microchip being found in a fibrosarcoma tumor and it seemed likely that the chip may have been the inciting cause of the tumor.  At the present time it seems likely that this only happens very rarely, even if it is true that the microchip was the inciting cause for the tumor. Microchips can migrate from the spot they are usually implanted between the shoulder blades. We have had one patient whose microchip migrated back almost to the hip region and several in which it migrated at least 5 to 6 inches from the injection site. This  isn’t a major problem in most cases but it could result in the chip not being read if it migrates far enough, particularly when a scanner is being used that isn’t the “native” scanner for that particular chip.

 

At the present time there are competing microchip standards and this has made it difficult for veterinarians and pet owners to decide whether to utilize microchips and which ones to use if the decision is to implant a microchip. There are four different standards for these chips;  they may transmit at 125 kHz unencrypted, 125 mHz encrypted, 128 kHz or 134 kHz. The international standard is 134 kHz but that is the least used frequency in the U.S. at the present time. If a pet has a microchip that transmits at  125 kHz and the animal shelter or veterinarian’s office where the pet ends up has a scanner that made to read chips that transmit at 134 kHz it is likely the reader will not recognize the lower frequency chip as easily. This can lead to missing the fact that a microchip is implanted, especially in shelter situations in which it may be difficult for the staff of the shelter to get really close to an anxious or aggressive pet to scan for a microchip. This is important, because microchips can migrate very far from where they are placed in some pets. The standard location for the chips is between the shoulder blades but we have seen them on X-rays as far back as the hip region, apparently having migrated there. The better attuned the reader is to the particular frequency the chip is transmitting at, the better the chance it will be found. Migration of the chips isn’t a huge problem, most stay in the approximate region where they were implanted but it does occur.

 

The ideal situation would be for all pets to be implanted with chips that transmit at a recognized frequency.  It seems logical that the best frequency to use would be 134 kHz since it is the international standard. However, there are about 15 million pets with chips that transmit at 125 kHz already, in the U.S.  If the standard is changed at this time the chips in these pets could be missed.  The companies that manufactured these chips have sued competitors with microchips operating at different frequencies in the past but I believe that argument is over.

 

To get around this problem the manufacturers of the newer microchips have been distributing scanners that can read all four frequencies of microchips.  It is likely that these readers will not read different manufacturer’s chips quite as well as the ones they were designed to work with. This means that the majority of chips will be recognized when a pet ends up in the shelter or a strange veterinarian’s office. The only catch being the few pets whose chips are difficult to read with scanners that can read multiple channels but are not as adept at picking up chips from a distance as the dedicated scanners are.

 

It is somewhat questionable whether everyone who might have to deal with a stray pet will have a microchip reader available. Bayer ™ , maker of ResQ ™ brand microchips is distributing 20,000 readers that can read all four types of chips. This seems like  it should be enough, but it is estimated that there are about 70,000 organizations and government agencies that are at least occasionally called upon to handle stray dogs or cats.  Until there is a real standard for the chips in the U.S. it will be likely that some lost pets will end up in situations in which there is not a scanner available to check to see if they have a microchip in place.  I don’t think that you can worry too much over this.  It is still better to make the effort than to do nothing at all.

 

The presence of multiple databases is also somewhat of a problem at the present time. I think that most of the shelters realize they need to call more than one database when they find a pet with a microchip implanted. Still, it would be much better if all the companies shared their databases in an open forum. I am not overly optimistic this will happen in the near future but hopefully they will eventually realize the need. 

 

I think that it is reasonable to use the type of microchip that your veterinarian implants. Most pets are lost close to home. You might want to double check with the local shelters to be sure they have readers for those types of chips. If you travel you just have to take a chance but it is at least helpful that scanners capable of reading all types of chips are making their way into the shelters as the companies compete to ensure that their microchips can be read.  The controversy is not over but you can still provide just a little more protection against losing your pet using any of the available microchips.

 

Microchip distributors I am aware of:

 

AVID  (125 mHz)

AKC CAR   (American Kennel Club Companion Animal Recovery)  (128 mHz)

HomeAgain  (125 mHz)

ResQ  (Bayer)  (134 mHz)

 

Finally --  remember that a collar and tag are still the first thing that most people are going to look for when they find a lost pet!

 

Thanks for your Support!
 
The VetInfo Digest is published by:
TierCom, Inc.
P.O. Box 476
Cobbs Creek, VA 23035.
 
The opinions expressed in this newsletter are those of Michael Richards, DVM., author.
Copyright  2007, TierCom, Inc.