Convenia for Cats: Sacrificing Safety for Convenience?

cat injection vaccination veterinarian

Most cat owners know that medicating a cat can be challenging. That’s probably why many veterinarians as well as cat owners celebrated when Convenia, a long-acting, injectable antibiotic, came on the market in 2008. Convenia is manufactured by Zoetis, formerly Pfizer Animal Health.

The idea of a one-time injection, instead of giving regular anitibiotics in pill or liquid form once or twice a day for two weeks or more, seemed like a great solution to the problem.

However, contrary to regular antibiotics, which are rapidly cleared from the body, Convenia stays in the body for two months or longer following injection, even though the antibacterial effects only last for two weeks. All drugs have some side effects. While some cats may do just fine with Convenia, others may have side effects ranging from mild to life threatening. And with a long acting drug like Convenia, there is no way to simply stop giving the medication – it’s already in your cat’s system.

Amber was one of those hard-to-pill cats. After careful discussion with my vet, I agreed to use Convenia following a dental procedure, which I’ve now come to learn is an inappropriate use for this drug. At the time, I only had misgivings about it because of its long-acting properties. Thankfully, she had no side effects other than some mild diarrhea, which is a common side effect of most antibiotics.

I recently came across a comprehensive article about Convenia by Dr. Lisa Pierson, the founder of, one of the best and most comprehensive websites about feline nutrition. In her article, Dr. Pierson weighs the pros and cons about administering this drug to cats:

Convenia: Worth the Risk?

Dr. Pierson’s article is a must read for all cat owners.

Editors’s note: comments about your  experience with Convenia are welcomed and encouraged. Comments that are disrespectful of others or malign the veterinary profession or individual veterinarians will be deleted. Please read our comment guidelines for more information.

References to other resources and/or websites or Facebook pages about Convenia which may be provided in the comments section are not endorsed by the site owners.

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761 Comments on Convenia for Cats: Sacrificing Safety for Convenience?

  1. Sarah
    August 2, 2020 at 8:44 pm (1 week ago)

    Iris, My heart goes out to you. I lost a beloved cat to Convenia in 2015 and would never give it to a cat again. One thing to be aware of: the drug is supposed to be active for 14 days but according to the US product information, the elimination period is over two months. (It’s worth reading
    the product information.) My cat was treated with various drugs including doxycycline, dexamethasone and buprenorphine during this period and eventually had to be put down in a severely toxic state. So I think one needs to be very careful about giving other drugs during this elimination period as there is a risk of interaction. Mary Ann’s experience is much more encouraging. It seems to me really good quality nutrition, probiotics and lots of love are probably best during the first few months when Convenia is still in her system. I really hope she pulls through.

  2. Iris Suarez
    August 2, 2020 at 2:17 pm (1 week ago)

    Thank you for sharing this information with us! I’m adding my comment in the hopes of continuing to spread info to other pet owners.

    I wish I’d done my research on this antibiotic. Instead, I trusted my veterinarian’s recommendation to use Convenia on my cat to treat a “possible” bacterial growth that he suspected “might” explain her recent vomiting spell. In retrospect, his rationale made no sense: why should an antibiotic for skin infections be the first course of treatment for a cat that has vomited only in the morning for a few days? But I trusted the advice, was assured all would be well, and I consented without doing research. I can’t tell you how badly I wish I could go back in time and stop myself from making this foolish, foolish mistake.

    My cat received the injection on 7/24/2020 and subsequently lost all appetite and became severely constipated. A week later, on 7/31/2020, I took her back to the same vet and she was given an enema, subQ fluids, and had pre-post xrays taken which revealed the fairly severe blockage (before) and the cleaned out system (after). She returned home and was dismally lethargic, could barely move, and exhibited clear signs of physical discomfort (accelerated breathing, stiffness, and dislike of touch–very alarming considering she is typically a cuddly cat).

    I have been syringe feeding her since Friday, and while she is finally appearing to be physically less uncomfortable, her appetite is still non-existent. One week to go, and I hope she is able to metabolize that Convenia within the next few days so that her appetite might start to return. I am telling myself to be patient, remain hopeful, and as long as I don’t quit on her, I hope I can carry her through the worst of this until she is able to rebound.

    I will be completing an AE report with the FDA, and I will contact that veterinarian to encourage him to stop using Convenia and submit an AE as well.

    Excuse the all-caps but I am scared and angry, and here’s the takeaway: VETERINARIANS MUST BE DISCOURAGED FROM USING THIS MEDICATION OUTSIDE OF IT’S CLINICALLY INDICATED USE. And even then, I wonder if it’s worth the risk for treating skin infections.

    To those of you also hurting and afraid because of how your dear kitty has reacted to this antibiotic, don’t give up–stay hopeful and keep taking care of your pet. Give them time to metabolize that garbage, support and nurture them if you can, and hopefully they will return to normal.

    • Mary Ann Farley
      August 2, 2020 at 4:54 pm (1 week ago)

      Iris, I know the heartbreak you feel. We all do.

      My Olive had the Convenia shot in July 2015, and I’m happy to report that five years later, she is thriving. However, in the beginning she was so traumatized by all of the sickness and doctor visits that it took almost a full year for her personality to come back. I did everything I could in that time to get her to calm down, like the diffusers, certain calming supplements, basically whatever was out there. When she regained her strength, we started with play therapy, which helped a lot.

      One thing that never recovered, however, was her appetite. For five years now, I’ve had to give her appetite stimulants daily. As you may know, if cats don’t eat for a few days, they can go into liver failure, so it’s not a question of “She’ll eat when she’s hungry.” No, she won’t, BECAUSE SHE’S NOT HUNGRY. That part of her brain was damaged.

      At first I gave her mitazapine, which works for three days, but it made her very agitated. It also made her very affectionate, which helped restore her loving personality, but after awhile, I changed her to cyproheptadine. It’s one-quarter of a pill daily, and I pulverize it then mix it will a little of Gerber’s chicken dinner baby food. I then just swipe it along the side of her mouth. Or I swipe it on her hind leg and let her lick it off.

      Once in awhile, the stress does mount of her getting it every day, even though she’s a pretty good girl about it, so I’ll give it every other day, or every two days. I’m actually supposed to give it to her TWICE a day, but I’m not going to do that to her. She’s been able to maintain a healthy weight just doing things this way.

      It’s not like she wouldn’t eat at all without the appetite stimulant, but she eats so little that she was losing weight rapidly there for awhile…from ten pounds down to 7.5. My vet and I knew we had to do something.

      Anyway, it was a long hard road for Olive and me, but she is truly the most loving cat I’ve ever known, so she was worth every penny and every effort. Oh, and just FYI, I give her Orijen Regional Red dry food, which is 90 percent protein. It’s expensive, but she loves it and it’s extremely high quality. She also likes her wet food, but it’s hard to find a healthy brand she’ll eat. After her medication, I can give her the good stuff, but after that it’s Fancy Feast, unfortunately. Good luck and let me know if I can help further.

      • Iris Suarez
        August 2, 2020 at 5:27 pm (1 week ago)

        Mary Ann, thank you so much for your reply. My heart breaks at all the stress and physical/emotional trauma your kitty (and you!) had to go through, but I also can’t express how encouraging your story is. I’ve been so worried since doing research online and reading about the poor outcomes, and it’s reassuring to hear that with consistent, loving care, a kitty can be nurtured back to their healthy self, for the most part.

        I have some of the mitazapine (it’s the transdermal ointment and goes on the inside of the ear), but I’ve been worried about giving her another medication while that antibiotic is still running its course. If it’s okay to ask, when did you start providing your girl with the appetite stimulant? Also, did you try probiotics and were they helpful?

        I’m currently syringe feeding my girl 38cc’s of Rebound daily, spread out across three feeding times (morning, midday, evening). She still won’t touch food, and I keep trying to tempt her with all feline equivalents of ‘junk food’ I can find–Sheba, Fancy Feast, tuna water, you name it. I’ve also tried sprinkling a packet of Fortiflora on the wet food, but that doesn’t pique her interest. I’m tempted to mix these probiotics in her evening serving of Rebound to try and support her gut microbiome, and wondered if you tried something similar in the past.

        Again, thank you for your kind words and support, and for sharing Olive’s story. I will try to find some Orijen in the meantime!

        • Mary Ann Farley
          August 2, 2020 at 8:03 pm (1 week ago)

          Oh, Iris…I’m teary these days to begin with, so your story really gets to me. I remember how devastated I felt…that same feeling of such deep regret, and seeing Olive change in an instant. I know you’re feeling the same. It’s pure heartbreak.

          As for when I started the appetite stimulant, I can’t honestly recall. For a long time, I did the Fortiflora and just kept presenting the food to her multiple times a day to get her to take bites. I never had to syringe feed her, but it was close.

          My opinion, I think, would be the same as yours…to let the med get out of her system before you introduce anything else. In the case of cyproheptadine, you could maybe start with 1/8 of a pill and just introduce it slowly in her syringe feedings (Just crush it with the back of a spoon and sprinkle it in). It’s simply an antihistamine, but it doesn’t make her tired or anything, and it does spike her appetite. I’ve never heard of the transdermal mirtazapine. I might ask her vet about that next visit, simply because the daily dosing of the cypro starts stressing her after awhile, like I said. I could maybe use both on and off.

          The only think I would be leery about with the mirtazapine at this point is that it can really affect their personalities. Most often, the cat becomes much more affectionate, which may help remind her of who she was before. But my pharmacist said his dog got aggressive on the drug. Can’t say I’ve heard of that with cats, but I’m just putting it out there.

          If it’s a matter of days for the drug to metabolize, I’d hold off on appetite stimulants for now, then introduce them slowly, whatever you use.

          Yes, Convenia should be pulled from the market. Also, common sense should just dictate that if your cat has a bad reaction, there’s nothing one can do to reverse it! That’s not for the cat guardians to think of on the spot when we’re going to the vet for advice. That’s the VET’S JOB….to think through these things!

          Anyway, please write to me anytime to check in. I wish I could figure out a way to give you my email address. Oh wait!—my web site is maryannfarley (dot) com and there’s a contact page there! That will go right to my inbox. But writing to me here is good, too.

          You’ll be in my prayers!

  3. Hank Armentrout
    June 18, 2020 at 11:17 am (2 months ago)

    Is there a form to fill out to do a report? My cat couldn’t move his front paw for a week and has been generally lethargic since he got this shot

  4. CarolK
    June 13, 2020 at 5:07 pm (2 months ago)

    I read about this shot before and got a little nervous.. so I opted for administering liquid antibiotics to my cat. It was difficult since it was twice a day.. and I am not sure it all went down. Long story did not work for long. 6 months later the Vet suggested the Convenia shot for my Kitty.. wow.. my cat and I had a rough week. I thought it was going to kill her.. she lost her appetite, sense of smell, and was clearly uncomfortable, hiding..and staring at the wall. Today (day 6) she is much better and eating. She isn’t well to begin with, and this might have put her over the top. She is 15 with IBD and a very high WBC. I would not recommend this shot for an elderly or weak cat.. Vet suggested giving her meds for appetite and maybe steroids.. I said no way until the therapeutic dose is cleared from her system..another week. Pretty stressful and scary.

    • Sarah
      June 14, 2020 at 9:36 pm (2 months ago)

      Hi Carol, I think you are very wise not to give your kitty any other drugs while Convenia is still in her system — and especially not steroids. Steroids have been known since 1994 to exacerbate the toxicity of other agents. (I quoted the reference for this, a study by Robert Sapolsky, on this thread a few years ago.) I lost a beloved 7-year-old cat in late 2015 after she had a bad reaction following a Convenia injection and was treated with various other drugs, including steroids, during the Convenia clearance period. I posted here (on 14 November 2016) a year after she died the lessons I had learned from that awful experience : “At the cost of Betty Boo’s life, I learned a number of things about Convenia that I had not known before: reactions are not always immediate and not always severe; repeated injections increase the risk of an adverse reaction; one of the major problems presented by the long elimination period is the risk of interaction with other drugs given concurrently or subsequently; and an adverse reaction that is not in itself life-threatening can become so if it is inappropriately treated.” Other people on this site have recommended probiotics. I didn’t find out about that in time, but natural unflavored yogurt is also worth trying; it has a lot of the good gut bacteria that is destroyed by antibiotics. I do hope she pulls through. Personally, I would avoid any other drug treatment during the clearance period (over two months, see US product information) and give her the most nourishing diet you can. Sarah

  5. Whitney
    February 6, 2020 at 9:41 pm (6 months ago)

    Hi everyone, I’m hoping I can find some reassurance. Last Friday (1/31) I rushed my 15-year-old kitty, Jonas, to a new vet because ours was out for his mother-in-law’s funeral. The night before, Jonas had started throwing up violently and that morning he had facial tremors. The vets were great and did bloodwork on him, everything came back perfect except his WBC count was elevated. They chose to treat him for nausea and an unidentified infection, and he was given injections of Cerenia and Convenia. I wasn’t spoken to about either of them, I just noted the names and decided to google them later to see if I should be aware of any side effects.

    Well, you’re all familiar with what comes up for Convenia. I have been a wreck and terrified I have sentenced my best friend to a horrible fate. I have had panic attacks and haven’t slept well in days. He has showed no negative reactions so far – he eats well, drinks well, is active, his bowel movements have produced some soft stool but nothing that seems super concerning. He hasn’t hidden or acted differently at all. But I can’t stop worrying. After reading through comments here I began giving him some of his brother’s probiotics (he takes them for IBS) to helpfully keep him on the right track.

    Do I just keep closely monitoring him and rush him in if there are any bad signs? I am praying that since it has almost been a week and he’s been his normal self that nothing bad will happen. I’ll never let it be given to him or any of my kitties again. I called my regular vet for reassurance and the nurse acted a bit annoyed with my worry, she said that his normal vet would have given him the same treatment and that they use Convenia all the time and have never had adverse reactions. He was apparently given a dose of it back in 2017 for a different illness and never reacted to it then, either, I just didn’t google it the last time.

    He did spit up a tiny amount today, but he had eaten some treats quickly. It was enough to make me freak out all over again but he hasn’t done it since.

    Any advice or reassurance would be great. I’m a very anxious person, especially with health anxiety, but for my babies it is at a completely different level. I am an absolute mess with worry and don’t know how to make it through the next 60ish days until it’s totally out of his system. Thank you all for sharing, I feel like I’ve let him down.

    • Ingrid
      February 7, 2020 at 5:39 am (6 months ago)

      I can understand how worried you are, Whitney. Since it’s been a week and you’re not seeing any signs of an adverse reaction, it’s probably unlikely that he will have any problems.

      • Whitney
        February 7, 2020 at 10:01 pm (6 months ago)

        Thank you, Ingrid. I appreciate it deeply. He’s done great still today but I’ll continue watching him vigilantly. I’ve also shared this space and other resources with my friends who are also cat parents so they know to avoid Convenia whenever possible. It’s just not worth the risk.


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