Convenia: Worth the Risk?
Lisa A. Pierson, DVM
5/21/12 update: I originally wrote this webpage in February, 2011. I was prompted to do so after receiving several reports of severe adverse reactions, including death, exhibited by cats and dogs after the administration of Convenia.
I continue to receive reports of possible adverse reactions. Note that I emphasize "possible" because it is impossible to thoroughly evaluate some of the reports due to so little information being provided. However, several reports have come through that outline cases of young, and otherwise healthy cats, that received only Convenia and no other medications were administered.
Please note that if you write to me about such an adverse event, all that I can do is continue to alert my colleagues and to strongly urge you to insist that your veterinarian file an adverse drug event (ADE) report with Zoetis (formerly Pfizer Animal Health).
In addition to your veterinarian filing a report, you should also contact Zoetis.
According to the FDA, any company receiving an adverse reaction report must report it to the FDA. I have no opinion or knowledge to comment on whether this is actually done in every case but I would strongly suggest that a follow-up complaint also be registered with the FDA. I am not willing to trust that every company will report every ADE report that comes to them.
Here is a link to information for consumer reporting of an adverse drug event with the FDA:
Information from Zoetis' website:
If a death occurs after the administration of Convenia and if Convenia is suspected as a possible cause, it is imperative that a complete post mortem exam, along with a microscopic exam of tissue samples, be performed. This is known as an "autopsy" or "necropsy".
As most people know, many drugs used in human and animal medical practice have been removed from the market after too many ADEs have occurred. Unfortunately, drug withdrawal from the market does not happen until many ADE reports are filed. Therefore, if your cat or dog has experienced a possible adverse reaction to Convenia, please do not let that reaction go unreported.
The health and lives of future patients depend on Adverse Drug Event reporting.
Convenia (manufactured by Zoetis) is an 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 antibiotics that 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 in some cases.
Most people are aware of the fact that all drugs have potential side effects with some being more significant/life-threatening than others so we need to be mindful of these side effects when any chemical is put into a living being, not just Convenia.
That said, with regard to Convenia, it is important to consider the fact that if a patient 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 (if other than acute anaphylaxis) 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 Convenia's drug insert. (The bold text is my doing.)
The most common reactions I have read reports of are anemia, tremors/ataxia, seizures, diarrhea, lethargy, anorexia, and death.
To repeat what I said above, all drugs have side effects but it is my opinion that Convenia is being administered far too often when there are safer choices available for nearly all cases.
In the summer of 2009, one of my favorite 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.
Note that Eddie is very easy to handle and it would have been no problem to medicate him orally.
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 and, eventually, made a full recovery.
Dentistry and Antibiotics:
Antibiotics are rarely needed for dental issues and this is an area where antibiotics, including Convenia, are very often overused. 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 of patients that 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, usually by removing it. 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 splinter out of your finger. In this analogy, the tartar on your cat's teeth, or an infected tooth, is the splinter.
Urinary Tract Disease and Antibiotics:
Let's jump to another area of feline health that often involves the over-use of antibiotics. Cats showing signs of urinary tract disease are often erroneously assumed to have a bladder infection. Clinical signs of a urinary tract problem can included 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 in error.
Most people assume that "UTI" stands for Urinary Tract Infection but the vast majority of 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. (See Urinary Tract Health for more information on this subject.)
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. "Cystitis" means inflammation of the bladder.
Therefore, in ~99% of these cases when the abbreviation "UTI" is used, the "I" stands for "inflammation" not "infection".
This means that a lot of cats are receiving unnecessary antibiotics and I am seeing Convenia used frequently in these cases.
This misuse 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.
Important point: Inflammation (cystitis) => pain yet so often these patients have their pain completely ignored.
Also consider that stress is a leading cause of cystitis and there are few things in life that are more stressful than pain so a vicious circle ensues. Another issue to consider is the stress involved for some cats when oral antibiotics are administered but, as stated above, 99% of young cats exhibiting clinical signs of urinary tract disease do not have a bladder infection and, therefore, do not need to be treated with antibiotics.
Back to the issue of Convenia....
Convenia is an injectable antibiotic and given the feline species' propensity for forming cancer at injection sites/sites of inflammation, I will always pick the oral route of administration if the patient can tolerate it. Granted, inject site sarcomas are not common but it is still an issue to consider.
Below is an excerpt from the Convenia drug insert but also note that these local adverse reactions can be seen with just about any injectable drug.
There is no doubt that Pfizer (now Zoetis) originally named this long-acting antibiotic "Convenia" because of the convenience for the pet owner. Unfortunately, because of this 'convenience', Convenia is being used within the veterinary profession with increasing frequency.
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, as noted above, 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 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 of assuming that just because your cat swallowed the pill he is safe. Cats usually swallow the pill just fine but then it gets stuck at the end of the esophagus - just before entering the stomach.
NEVER USE clindamycin (Antirobe) or doxycycline tablets. These medications are highly inflammatory and have caused fatal esophageal strictures.
2) Flavored liquids - Clavamox comes as a liquid which most cats tolerate well. Medications can also be compounded by a compounding pharmacy into fish or chicken flavors. Clindamycin (Antirobe) also comes in a liquid and while it tastes pretty nasty, most cats don't hold a grudge too long after its administration.
3) Injectable - If using this route, vary the location to keep local inflammation to a minimum and ask your veterinarian if the medication can be diluted with a sterile solution.
(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 two 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 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, 1/5 - 1/4 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 2 small pieces of the pill - each wrapped in 1/5 of a PP. He gobbled up the 2 ‘treats’ readily (one at a time) and I gave him the other three 1/5 pieces as a treat 'chaser' and to stimulate salivation which helps to move the pills into the stomach.
If you are breaking pills apart, be careful to avoid getting any pill powder on the outside of the PP.
Before attempting to use PPs to administer medication, try taking 1/5 of a PP and rolling it up into a ball without a pill inside 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.
Another option (because most people don't have FortiFlora available) is to take some dry treats such as Temptations or Pounce treats and crush them up and roll the PP in the treat 'dust'.
As an aside, if you have a dry food addict, please see the Tips for Transitioning Dry Food Addicts to Canned Food. As noted on my 'Tips' page, I also sprinkle a bit (as little as 1/20 - 1/10 of a package) of FortiFlora on food to entice cats to eat if they are being stubborn about trying a new food such as when trying to get a dry food addict to eat canned food. I always have FortiFlora in my home since it comes in very handy.
Some people also have good luck wrapping a 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.
As noted above, 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.
Having voiced my strong opinion about the overuse of Convenia, are there any patients that I would consider using it for? Yes - but it would be a very rare situation and the risks involved would be discussed with the client so that they could make an educated decision.
Before deciding on the best antibiotic to use - or whether to use an antibiotic at all - several questions need to be asked:
Culture/sensitivity (C&S) tests can be very expensive which is why many veterinarians opt to not run them and this is understandable. That said, just be aware that a C&S is the best option when dealing with these cases. It is also important to note that many cat owners end up spending far more money in the long run 'chasing their tail' with needless, and often harmful, antibiotics when dealing with sterile cystitis, or with the wrong antibiotic in the case of some infections.
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 secondary to a bite wound from another cat. A '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 were successfully treated by simply lancing and draining and the cats did very well when immediately released after they woke 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. This is understandable because most veterinarians have not observed an adverse reaction in their patients so they have no reason to be concerned. In these cases, 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 discuss this issue with your vet in advance of any possibility that Convenia may be administered. Keep in mind that it is often administered after dental procedures.
In addition to verbal communication, I would also urge you to 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 put in your cat's chart "NO METACAM without discussing the pros and cons first". Metacam is a non-steroidal antiinflammatory drug (NSAID) that has the potential to cause kidney damage in cats. The manufacturer recently added a ‘black box’ warning stating that it is not to be used in cats past a single injection. 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 but I feel strongly that more critical thought needs to be applied to the use of this drug. As stated above, there are other, safer, options and, in addition to their increased safety, these other antibiotics are often more appropriate choices in terms of their bacteria-killing spectrum.
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, keep in mind that there have been many drugs recalled from the human and veterinary market over the years but not until a significant number of patients suffer from adverse effects.
Whether Convenia is ever pulled from the market or not remains to be seen but, for me, its risks far outweigh its rewards except in very rare situations.
Created: February, 2011
Partially updated February 2013
Lisa A. Pierson, DVM
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.