Convenia Injection Chosen Over Oral Antibiotics

Convenia, the long-acting antibiotic injection that maintains antibiotic levels in a dog or cat’s bloodstream for up to two weeks is the hot topic this week.

Let’s look at another case in which Convenia worked out well.

Fritzi is a Shih Tzu who weighs 20 pounds and has a urinary tract infection. A urinalysis revealed that she had round bacteria, cocci,  in her urine. We began an oral antibiotic that has a wide spectrum of effectiveness for cocci, and simultaneously submitted a sample for a bacterial culture and sensitivity test  to a laboratory.

Five days later we had results and the sensitivity portion of the test showed that the antibiotic we first chose was effective.

We called Fritzi’s owner to inform them of the results and to ask them to pick up additional antibiotics so that we could have a total of three weeks of antimicrobial therapy.

They were happy to hear that the organism was not resistant, but had a comment about the medication Fritzi was already on. “She’s been vomiting intermittently since she started it. Not every time, but at least once a day. We tried it with food and on an empty stomach, but nothing made a difference.”

Vomiting, with or without diarrhea, are sometime complaints with oral antibiotic therapy. Many antibiotics are associated with these problems.

We gave Fritzi’s owners three choices:

  1. One was to stick with the same antibiotic but begin giving yogurt several times daily in an attempt to appease the gastrointestinal (GI) tract with beneficial bacteria. The technique works in about 50% of cases and has the advantage of allowing Fritzi to continue to take the same inexpensive antibiotic. Two more weeks of this antibiotic would cost $21.25.
  2. Option two was to change to a different antibiotic. The next best antibiotic infrequently causes GI upset, but costs more. Two weeks for a Fritzi-sized dog costs $61.40.
  3. Option three was to give Fritzi a Convenia injection. The active ingredient in Convenia, cefovecin sodium, is a cousin to the first antibiotic we started for Fritzi, but injectable forms almost never cause GI upset, so we should have excellent results in treatment without side effects. The cost? $65.00

How to decide?

If cost were the only factor it might be worthwhile to try to use the original antibiotic, recognizing that there is a 50% chance that vomiting might continue, which would lead to a change of medication anyway and loss of the $21.25.

Weighing the other two options becomes what modern parlance would call a no-brainer. Two weeks of pills twice daily versus no pills, for almost the same cost?

And nearly identical effectiveness.

While the final decision is always the client’s choice, most people would choose the Convenia injection, I’m sure.

I know I would for my own pet.

See you tomorrow, Dr. Randolph.


  1. I know this post is several years old, but I wanted to add my story. My cat Mau-Mau is 12 years old. Three weeks ago we took him in for what we thought was an oral abscess: swollen upper lip, green puss in mouth, pain to the touch. Being that this is his time of year to eat mice coming into the house, I figured that was the cause.

    The vet could not find the puncture or head site of the abcess. He went ahead and gave my cat the Convenia injection. It showed up on the bill as 11 doses? I’m assuming that is due to body weight. He also was given an IV of fluids, due to his lack of eating from the mouth pain.

    The first day home he slept due to the anesthesia. The second day he started vomiting clear liquid and foam. The third day, he still had no interest in water or food. I tried feeding him wet food through a syringe and he threw it up within a half hour. I continued for the next few days trying to feed him with a syringe and give him water, but he just couldn’t hold it down.

    I finally called the vet and picked up cans of Hills Prescription Diet A/D canned food, as well as Cerenia 16mg tablets for vomiting. After giving him the Cerenia, he was able to hold down his food for almost 2 days. Then vomiting would start back up. I was able to space the Cerenia tablets out to every other day.

    Let me make it clear, during this past entire 3 weeks, I have had to feed him hourly with a syringe, both food and water. He has zero interest in food, even on Cerenia. If I give him more than one syringe of food/water at a time, he will vomit (even while on Cerenia).

    Sigh. Again. This has been going on for 3 weeks now. On top of his lack of appetite, he is also bound to his bed- meaning all he does is lay down and sleep. I am not sure if the cause, but after reading about Convenia side effects and how long they can last, I’m wondering if that’s the culprit.

    Christmas is almost here and everywhere is closed. I’m going to continue my routine until my vet is open. I think I have only helped him to just get by. Thankfully no yellowing of the ears or eyes! I know they will want to do blood tests. Hopefully they might have a longer acting solution to his nausea and non interest in food/water. Fingers crossed that he will be okay and it’s nothing serious. I call him my little soul mate. It will break my heart if I lose him.

  2. I am incredibly worried about the Convenia shot after all the scary reviews. I realize these are all from the Internet (pssht) and so are intentionally the bad ones, but it still makes me nervous. My cat Fritz went into the veterinarian’s office 10 days ago and was diagnosed with a UTI (I’m not sure if it was just crystals or if there was actually bacteria involved) but he received the Convenia shot. Before the shot, he was peeing all over the place, had blood in his urine, and was meowing all the time. Since the shot, he has been peeing normally and hasn’t been meowing as much. However, there is a distinct change in his energy level. I took him into an ER veterinarian last night to make sure the UTI hadn’t become a blockage, but they found everything to be normal. Maybe his lethargy comes from just being sick? But there is a distinct difference in the way his eyes look- they are droopy and he seems “spacey.” He also sleeps all. day. long. He is about three years old, and I have never seen him sleep so much before. He is eating a TON (special SO diet- about a can and a half a day: he is a seven lb cat), still peeing normally, and sometimes wants to play, but not often. Is there any reason for me to take him back to the veterinarian? Or should I continue to wait it out?
    Thank you so much for your love of animals!

    • Take a deep breath. Whenever you go online to look up medical information, keep in mind that 64% of the medical information on the Internet is either outdated or just plain wrong. And, that’s not counting the “stuff” that is written by the opinionated, uninformed element. By contrast, when something we’ve published on becomes outdated, we take it down! There is a lot of hoopla about Convenia, but how much has been substantiated by laboratory testing and necropsy? Very little. In the years I’ve administered Convenia for both on-label and off-label uses, I have had ONE (1) bad outcome, which was clearly an allergic reaction, was treated and the patient did great. I have spoken to Pfizer Animal Health (now Zoetis) extensively about the safety parameters of Convenia. They are legally bound by the Federal Food and Drug Administration (FDA) to disclose problems with medications. Usage history simply does not match the vitriol on the Internet. There is no reason to suspect your kitty will have any problems from Convenia. If you would like to read more of what we have posted about Convenia, simply type Convenia into the SEARCH window in the upper right hand corner of this or any page on and press the Enter key. I have written about it extensively because it is a wonderful tool in the veterinarian’s toolbox that does wonders for the vast majority of patients for whom it is used.

      • Convenia saved my dogs life at a fraction of the cost I spent for 2 days of IV antibiotics at a teaching university.

  3. My cat had Convenia injection today at 1pm and he has not had any problems with eating or drinking. Is this a sign he is not going to have all of the reactions other people are talking about?

    • Funny that you would write when you did. A colleague and classmate called me the same day, asking about Convenia. He had never used it, then ordered his first bottle. But, when it arrived he was concerned about some of what he had read on the Internet. His question for me was, “Should I send this back? Is the first cat I give it to going to die?” I assured him that my experience has been completely different from much of what one reads on the Internet. I have had one reaction to Convenia, and it was a typical allergic reaction: hives, redness of the skin and itchiness. It resolved within a few hours after an allergy-blocking injection. Another of our classmates practices near our hospital. We talk at least twice weekly and he has never had a single bad response to Convenia. However, this is the experience of two doctors. Others who have had different experiences need to follow the instructions in this post: Report An Adverse Event. It’s the only valid way to identify true problems with any medication. Most of the negative reports one reads are anecdotal, stories with no gathering of factual, scientific/medical facts. I trust your kitty is doing well, but would like to hear back from you.

    • Your Convenia comments about the allergic reaction and subsequent good outcome of treatment for one of your patients is good news. However, I am skeptical. My vet said their is no antidote for an allergic reaction to Convenia. Since it remains in the body the patient dies. What did you use to combat that?

      • The bacteria-killing activity lasts 14 days, but the allergic reaction can be stopped with one’s favorite intravenous corticosteroid, with or without an antihistamine. Even though I wrote that post some time back, it remains the only problem case I’ve had with the medication, and we use it a lot. Thanks for reading

  4. Dr. Randolph, I had my little boy put to sleep today. I just couldn’t ask him to endure any more. We never really decided he had FIP, but it was obvious he was getting worse and was probably not going to recover. At least he got to spend a little time at home. The weather was rather nice yesterday, so I let him sun himself outside for a few minutes. I think he enjoyed that. I wonder if the Convenia triggered the FIP somehow? I don’t know if it was the right thing to do, but I let Pfizer have his remains for autopsy. I’m not expecting much from it, but I’m hoping they’ll find something to help other animals. I’ve read too many sad stories connected with Convenia injections to believe it’s a coincidence.
    Okay, I’m done here. Thanks again for the kinds words. I guess I did need your sympathy after all.

    • I know you are heartbroken. You did all the right things. Perhaps you would be comforted by visiting this post on grieving. I wrote it after I lost my own cat, Sally, to FIP. She was a totally-indoor cat who probably got the virus through our back porch screen, fighting with stray(s), thus sharing nasal and/or saliva droplets through the screen. She was such a delight, and only 12 years old. That was 1992, and I still miss her. You can have no regrets at this point, because you did everything possible.
      PS: I would love to see the Pfizer report, if you don’t mind sharing it I can send you my mailing address by email.

  5. Dr. Randolph, I brought my kitten home yesterday. Wow, nursing a sick cat is difficult! His belly is still big, but his temperature has been normal for several days. The veterinarian is cautiously optimistic; however, she has not ruled out FIP. I’m just hoping he’s not completely miserable, and that being home will have something of a healing effect on him. I didn’t have a question. I just wanted to give you an update. Happy New Year!

    • Lainey, you have been very brave, and very dedicated. My hat is off to you. My heart is breaking along with yours. Thank you for having the courage to “nurse a sick cat.” It is hard work. And thank you for the update. We really like knowing what is going on with pets (and readers) we have bonded with.

  6. I’m very sorry to hear about the loss of your patient today and the well-loved pet you lost in July. She was lucky to have you for her human caretaker. I mentioned your response about the textbook FIP to my veterinarian, and she said there are some things about my little guy’s case that are not textbook. She explained what they are, but it’s all pretty much over my head. I was just glad to see him feeling better this evening. We’ll see how things go this weekend. For my part I’m ready for whatever comes. I’d just like to say I think he’s a rather remarkable and charming little cat, and I’m happy to know him. I probably won’t write again, unless something unusual happens. Thanks again for the kinds words and advice.

    • The reason I included the parenthetical phrase “despite not having examined him myself” is that there are things to know when one is not present that can be crucial in a case, which make the difference between knowing when one is a “textbook” case and when it isn’t. From what I can tell your veterinarian is doing an exceptional job, and you are fortunate to have her. Thank you for keeping me updated and I want you to know you can write to us any time at all.

  7. Sorry, Dr. Randolph, I don’t understand the thinking here. Why bother to reduce his fever if he’s got a fatal disease? Wouldn’t it be more humane just to have him euthanized? He doesn’t have to hang around for my benefit. And despite that fact that he seems to have a textbook case of FIP, should I give the blood transfusion a chance to do some good? I need advice, doctor, not sympathy. Although I do appreciate the kind words. If he were your cat, what would you do?

    • All you can hope for now is to buy some time. The transfusion may perk him up, the steroids may reduce his fever, the purpose of which is to make him feel better in the hopes that he might eat. Realistically (despite not having examined him myself), a little time is all you can hope for. The only value to that time is to give him and you time to say goodbye. If you feel you’ve already done that, and have already, emotionally, let him go, then there is no good argument against euthanizing him now. What would I do? I can tell you what we did when we had to let our Martha go at the end of July. She lingered for a month, even though I still don’t know how. She drank, but wouldn’t eat. Still, she seemed happy and wasn’t suffering in any way. We prayed with her and for her daily. On her last night I looked for a sign to know whether she was going to “go” on her own or whether she needed my help. Right at bedtime she began to wobble and shake. It was the first physical sign of “disorder” she exhibited. I made the decision to euthanize her at that point. Or, maybe she made the decision. Again, if you feel you’ve said your goodbyes, consult with his doctor and this may be the right time. I’m so sorry. There is never a good time to have to let go of a friend. Christmas just seems like the worst possible time. (I lost a patient of my own today.)

  8. Thank you for your comments, Dr. Randolph. The veterinarian has contacted Pfizer. It was one of the first things she did. The test results for autoimmune issues came back negative. She received cytology results today, and the fluid from his abdomen shows high protein levels but no fibrin. I can’t recall if we’ve received any results regarding his liver. She mentioned the PCR, but I think we’re going to give him a few days to see how the transfusion affects him. If he improves we may move on to steroids to help with the fluid. She says his temperature is holding steady at 104.5 and his belly is not much bigger than it was yesterday. If he declines, then she thinks that would be a pretty good indication that he has FIP. So now I guess we wait. What do you think of this plan? I was so upset after reading about FIP, I was ready to have him euthanized this morning. I don’t want him to suffer in any way. He’s been through enough.
    I also wanted to mention he’s not really eating now. I was told he didn’t eat anything during the night, but he had been eating somewhat up to that point. And the fluid in his abdomen is not affecting his breathing, so it’s not so much that it’s crowding his lungs. I’ll be going to visit him in about a half hour. I almost don’t want to disturb him, but the doctor thinks it’s more helpful than harmful.

    • Lainey, I didn’t want to rain on your parade, but if there was ever a “textbook” case of FIP, your baby is it. Steroids are certainly worth a try, and might even break his fever, or at least reduce it. I am so sorry. I know you have been dedicated to him and your words clearly indicate how much you love him.

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