____________________________________________________________________Convenia: Worth the Risk?
Lisa A. Pierson, DVM
Convenia (manufactured by Pfizer) is a relatively new injectable long-acting antibiotic that is labeled for the treatment of skin infections in cats and dogs. It exerts its antibacterial effects for approximately 1-2 weeks but stays in the body for over 2 months.
This is in contrast to non-repositol antibiotics which are rapidly cleared from the body and need to be administered 1 - 2 times per day.
Given how difficult it is to medicate some cats, this 'long-acting' property sounds great, right?
Unfortunately, the old adage, "If it sounds too good to be true, it probably is", rings very true with respect to the use of Convenia.
It is important to understand that all drugs have side effects with some being more significant/life-threatening than others so it is very important to consider these side effects when any chemical is put into a living being.
Consider the fact that if your cat has an adverse reaction to Convenia there is no way to retrieve this long-acting drug from his body.
If an adverse reaction occurs after a short-acting drug is administered, the patient has a much greater chance of living through the event because the body will clear the offending drug, hopefully, within hours - not months, as is the case with Convenia.
Note what is stated on the Pfizer website. (The bold text is my doing.):
CONTRAINDICATIONS: CONVENIA is contraindicated in dogs and cats with known allergy to cefovecin or to β-lactam (penicillins and cephalosporins) group antimicrobials.
Anaphylaxis has been reported with the use of this product in foreign market experience. If an allergic reaction or anaphylaxis occurs, CONVENIA should not be administered again and appropriate therapy should be instituted. Anaphylaxis may require treatment with epinephrine and other emergency measures, including oxygen, intravenous fluids, intravenous antihistamine, corticosteroids, and airway management, as clinically indicated.
Adverse reactions may require prolonged treatment due to the prolonged systemic drug clearance (65 days).
FOREIGN MARKET EXPERIENCE: The following adverse events were reported voluntarily during post-approval use of the product in dogs and cats in foreign markets: death, tremors/ataxia, seizures, anaphylaxis, acute pulmonary edema, facial edema, injection site reactions (alopecia, scabs, necrosis, and erythema), hemolytic anemia, salivation, pruritus, lethargy, vomiting, diarrhea, and inappetance.
Why am I devoting an entire page to just one drug? It is because there have been too many reports of otherwise healthy cats dying or becoming very ill (seizures, anemia, diarrhea, etc.) within a few days to 1 week after receiving even just a single injection of Convenia.
Some people may question the definition of "too many" but here is my bottom line: If it happens to your cat, that is a 100% failure rate and it matters very little what the failure rate is among thousands of other cats.
To repeat what I said above, all drugs have their side effects but the point that I am trying to make with this article is that if a safer antibiotic is an option (true in almost all cases), why not choose it? This is exactly what I am trying to make the reader aware of: There are safer choices other than Convenia and veterinarians need to discuss the options with their clients - or, if Convenia is chosen as a treatment, the client needs to be made aware of the risks involved.
We need to stop referring to Convenia as a "wonder drug" which it has been called many times since it came onto the market a few years ago.
In the summer of 2009, one of my favorite long-distance consulting patients ("Eddie") came close to losing his life within days of receiving a Convenia injection. Eddie was a very healthy cat that went in for a routine dental cleaning. Unfortunately, his veterinarian decided to give him a shot of Convenia thinking that it would be easier for the client than giving pills.
Ironically, and very sadly, this patient did NOT even need ANY antibiotics which made his life-threatening adverse reaction even more difficult to handle emotionally for both the owner and myself. (Also note that even if Eddie did need antibiotics, Convenia is not an appropriate first choice antibiotic to use for dental issues as discussed below.)
Eddie stopped eating and had severe diarrhea within a couple of days of receiving the injection. Having just read about two cats dying shortly after receiving Convenia injections, I suggested that she take him to an advanced-care veterinary facility immediately, which she did.
To make a long story short, Eddie was severely anemic (one of the known side effects of the class of drugs that Convenia belongs to). After a 1 week stay (including blood transfusions) in the Critical Care unit of the specialty hospital…and $6,000 later, Eddie was discharged and was doing well 1 month later.
While we are on the topic of antibiotics and dentistry, please note that antibiotics are rarely needed for dental issues and this is an area where antibiotics are very often abused. Dr. Frasier Hale is a board-certified veterinary dental specialist and has written a paper for his website entitled Antibiotic Use in Veterinary Dentistry.
Here is a quote from that paper: "In general, antibiotics are vastly over-used in veterinary dentistry, often to the detriment of the patient."
I share Dr. Hale's frustration but want to take it one step further as it pertains to Convenia. IF it has been determined that a patient fits into the fairly 'rare' dental category and does need antibiotics, Convenia is NOT an appropriate first-choice antibiotic for any dental issue since its spectrum of antibacterial activity is not targeted toward the bacterial species that normally live in the oral cavity.
Antibiotics vary significantly in their ability to kill various species of bacteria so it is important to match the correct antibiotic with the target infection.
When it comes to dental care, the most important issue is to remove the bacteria by cleaning the teeth (under general anesthesia - not by using anesthesia-free services) and addressing any infected tooth by removing it or doing root canal therapy. The answer is not to use antibiotics in an attempt to kill the bacteria which is often unsuccessful and even if it is successful, it will only be temporary as outlined in Dr. Fraser's paper.
Using an infected splinter of wood stuck in your finger as an analogy - you would not consider pouring antibiotics over your finger, right? Your answer would be to get the darn splinter out of your finger! In this analogy, the tartar on your cat's teeth, or an infected tooth, is the splinter.Let's jump to another topic that involves a significant pet peeve of mine and that is the over-use of antibiotics in cats that are showing urinary tract signs. (e.g. urinating small amounts frequently, blood in the urine, licking their genitals, urinating outside of the litter box due to a litter box aversion which developed secondary to pain, etc.)
Notice that I did not use the abbreviation "UTI" which is so often thrown around erroneously.
Most people know that "UTI" stands for Urinary Tract Infection but so many cats that are showing these UT signs do NOT have an infection yet they often leave the veterinary clinic with antibiotics and no culture and sensitivity to prove that an infection even exists.
It has been shown that when otherwise healthy cats (no kidney disease, diabetes, or hyperthyroidism) that are showing urinary tract signs have their urine cultured, only 1% will have a bladder infection. The other 99% are suffering from sterile cystitis. "Sterile" means that no infection is present. This means that a lot of cats are receiving unnecessary antibiotics!
Therefore, in ~99% of the cases when the abbreviation "UTI" is used, the "I" stands for "inflammation" not "infection".
This abuse of antibiotics leads to more resistant strains of bacteria ("super bugs") being produced which puts all living creatures (humans and animals) at risk. The pharmaceutical companies then need to keep coming up with new ways to fight life-threatening infections caused by these resistant bacterial populations.
Please see my Urinary Tract Health page for further discussion outlining how these patients are often not properly treated.Please understand that you cannot predict which patient is going to have an allergic or anaphylactic reaction, or have seizures or become severely anemic, but just know that they are life-threatening side effects and, as noted on the Pfizer site, any adverse reaction is going to have much more serious consequences when a long-acting (repositol) drug is the cause.
It is also very important to note that the cat has a higher tendency to form tumors at any site of inflammation - from any cause - when compared to other species.
Many people are aware of VAS (Vaccine Associated Sarcoma) which are highly malignant and often rapidly fatal tumors that form at the site of vaccines - especially ones that have adjuvants in them - but sarcomas can also form at the site of an injection of other medications."Chicken" is a special kitty that ended up with a VAS after an adjuvanted rabies shot was given in the scruff area. In addition to aggressive surgery, she has had to go through radiation and chemotherapy treatments. ***Please note: Vaccines are NOT to be given in the scruff area. They are to be given as low in a limb as possible. This is to allow for amputation if a VAS occurs.
Note what the Pfizer drug insert states:
injection site reactions (alopecia, scabs, necrosis, and erythema)
As a veterinary practitioner, I think long and hard before I inject anything into a cat because of their propensity for forming cancer at injection sites. While inject site sarcomas are not common, If given a choice between administering a medication orally versus as an injection, I will always pick the oral route if the patient can tolerate it.
There is no doubt that Pfizer named this long-acting antibiotic "Convenia" because of the convenience for the pet owner. However, this 'convenience' can come at a very high price to the patient if an adverse reaction is experienced and I am witnessing this antibiotic being mis-used/abused within the veterinary profession more frequently because it is so 'convenient' to use.
One argument that I hear my colleagues use to justify the high volume use of this drug is that owner compliance is often seriously lacking. It is a well-known fact that many pet owners are not very good about medicating their pets on a consistent schedule. (I confess.....I am often terrible about medicating my own cats on a proper schedule and I should know better!)
This can lead to treatment failures, as well as resistant bacteria being selected for when antibiotics are not given as prescribed. Therefore, some veterinarians are opting for Convenia to get around this issue.
Of course, everyone (myself included) wants to take the easy road when it comes to medicating cats and while giving one shot of Convenia is very enticing, I strongly urge anyone reading this to not go down that path because there are much safer options in almost all cases.
For instance, antibiotics such as amoxicillin, clavamox, and clindamycin are cleared from the body rapidly which, as noted above, is an important consideration if any adverse effect manifests itself.
I understand very well that some cats are hard to medicate but other options are often not explored and Convenia is used as an easy way out of the situation.
There are 3 forms of antibiotics that can be used:
1) Pills - If using pills, please see my Pilling Cats and Dogs article for reasons why you never want to 'dry' pill any animal. Don’t make the mistake in assuming that just because your cat swallowed the pill that he is safe. Cats usually swallow the pill just fine but then it gets stuck at the end of the esophagus....just before the stomach.
2) Flavored liquids - Medications can be compounded by a compounding pharmacy into, typically, fish or chicken flavors.
3) Injectable - If using this route, vary the location to keep local inflammation to a minimum.
(The transdermal route - via an ointment applied to the ear - is not effective for antibiotics since adequate blood levels are not reached.)
Personally, I hate pilling cats but some cats are more amenable to pilling than they are to swallowing liquids so each case has to be considered individually. Just be sure to never 'dry' pill any animal.
Pills always need to be 'chased' immediately with 4-6 cc of water (using 3/4 - 1 cc at a time and preferably with a flavored water to enhance patient compliance) or the patient needs to eat some food immediately after receiving the pill. Again, please see my Pilling Cats and Dogs webpage for more information.
Flavored waters can be in the form of chicken or beef broth or you can make your own tuna water by adding a can of tuna to 2 - 3 cups of water and then mashing up the tuna….letting it sit for 10 - 15 minutes…. then pouring the water through a strainer into ice cube trays for a convenient way to store the 'chaser' liquid. (3 cups of water fills 2 16-cube trays.)
Rather than pill a cat, I prefer using liquid antibiotics or, if clavamox is being used, I have great luck with crushing the pill and mixing it into canned food. This is how I have treated many feral cats in the past and I have never had a cat refuse to eat clavamox tablets crushed and mixed well into canned food. (See Feeding Your Cat: Know the Basics of Feline Nutrition for reasons why dry food is not a healthy diet for cats.)
Another great option is the use of Pill Pockets (PP). Most cats love PPs and will readily eat them but be aware that you should never use a whole Pill Pocket because they are too big and most cats won't swallow them whole which is our goal. Instead, they will bite down on them and then that will be the last time they will ever eat a PP!
When using PPs, use just enough dough to wrap around the pill. The smaller the rolled up ball is, the more apt they will be to swallow it whole. Often, 1/3 of a PP works well but it depends on the pill size. If you can split the pill into smaller pieces, that lowers the chance of them biting down on a larger PP. When one of my cats needed to be medicated, he got 3 small pieces of the pill - each wrapped in 1/3 of a PP. He gobbled up the 3 ‘treats’ readily.
If you are breaking pills apart, be careful not to get any pill powder on the outside of the PP.
Before attempting to use PPs to administer medication, try taking 1/3 of a PP and rolling it up into a ball without a pill inside just to see if your cat will eat it. If he won't, then try rolling the PP piece in parmesan cheese.
Another one of my favorite tricks is to roll the PP in FortiFlora which is a probiotic made by Purina. This is my favorite trick to get dry food addicts switched over to canned food since the probiotics are contained in a very enticing animal digest, liver-based powder which is what they spray onto dry food to make it so palatable to cats.
As an aside, if you have a dry food addict, please see the Tips for Transitioning Dry Food Addicts to Canned Food.
I also sprinkle a bit (as little as 1/10 of a package) of FortiFlora on food to entice cats to eat if they are inappetent for any reason or are being stubborn about trying a new food such as when trying to get a dry food-fed cat to eat canned food. I always have FortiFlora in my home since it comes in very handy!
Some people also have good luck wrapping bit of cream cheese around small pills but I have better luck with Pill Pockets since cream cheese is a bit sticky and not as easily swallowed…leading to the cat tasting or biting down on the pill.
Most antibiotics can be formulated into flavored liquids by a compounding pharmacy. These preparations are usually more expensive than pills but are often well-worth the added expense.Ok - so having voiced my strong opinion about the overuse/abuse of Convenia, are there any patients that I would consider using it in? Yes - but it would be a rare situation and Convenia would never be used without making sure that my client was well aware of the risks involved so that they could make an educated decision.
Before deciding on the best antibiotic to use, several questions need to be asked:
1) Does the patient have a proven bacterial infection that warrants the use of antibiotics?
A. This means culturing the urine of any patient suspected of having a urinary tract infection and not blindly putting every cat on antibiotics that is showing urinary tract signs.
B. The "warrants the use of antibiotics" part of that sentence addresses the overuse of antibiotics in dental patients.
2) If an infection has been proven, has a sensitivity (aka "susceptibility") test been run to provide a list of appropriate antibiotics to use?
3) If a sensitivity test has been run against the bacteria that were cultured, which is the safest antibiotic to use?
4) Is the patient absolutely impossible to treat with an oral antibiotic using any of the methods outlined above? (Again, note that many feral cats have been successfully treated with clavamox tablets crushed up and mixed into canned food.)
5) Has the patient shown intolerable side-effects from all of the short-acting, safer antibiotics on the list?
6) Is the choice of Convenia being made with the patient's best interest in mind or is it being selected with the client's 'convenience' issues as a priority?
The use of Convenia in feral cats that are being TNR'd (trapped, neutered, returned) poses a dilemma; this situation is not cut and dried.
It is not unusual for feral cats that are brought to a vet for spaying/neutering to also have an abscess present - usually from a bite wound from another cat. This is when the 'weighing of risks' comes into play when deciding whether to simply lance the abscess and drain it and not give Convenia, versus lancing, draining, and giving Convenia prior to release.
Personally, I will continue to opt for no Convenia because long before Convenia was available, many abscesses have been successfully treated by simply lancing and draining them and the cats have done very well when immediately released after they wake up from their surgery. This is a more comfortable path for me to take rather than to administer Convenia to a patient that will be lost to follow-up since re-trapping a feral cat is not logistically feasible. If that cat has an adverse reaction, he is on his own.
One final note: It is not unusual for veterinarians to give Convenia to patients without discussing it with the client first. Often all you will see is "Convenia" on your bill and it will be too late to voice your concerns.
It is for this reason that I highly suggest that you ask that "NO CONVENIA" be written on your chart in red to make sure that it is very visible to any veterinarian caring for your cat.
I would also take it one step further (since written notes in a chart can be missed) and verbally let your wishes be known to each veterinarian who cares for your cat.
I would also put in your cat's chart "NO METACAM" which will be the subject of my next webpage. Metacam is a non-steroidal antiinflammatory drug (NSAID) that can cause kidney failure in cats. The manufacturer recently added a ‘black box’ warning stating that it is NOT to be used in cats. That said, it may be considered for use in arthritic cats that have had their quality of life enhanced by it. Again, all drugs have to be considered for use in light of their risks versus their rewards.
In closing, I would like to point out that, of course, not every cat that receives a Convenia injection has an adverse reaction otherwise the drug would not be on the market. But that said, everyone has to decide what level of risk:reward ratio they want to deal with especially in light of the fact that there are other - safer - options. For me, Convenia's risks far outweigh its rewards except in very rare situations.
Created: February, 2011
Lisa A. Pierson, DVM
[email protected]
Information on this site is for general informational purposes only and is provided without warranty or guarantee of any kind. This site is not intended to replace professional advice from your own veterinarian and nothing on this site is intended as a medical diagnosis or treatment. Any questions about your animal's health should be directed to your veterinarian.
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