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Convenia is a single injection of a long acting antibiotic, given under the skin, that treats certain bacterial infections for about 14 days without a pill going down at home. For a cat who can't be medicated, or a dog whose owner is going to lose that fight by day three, it solves a real problem.
The trade off is that you can't take it back. It works for two weeks, but it stays in the body for up to 65 days.1 Once it's in, it's in.
That one fact should shape the conversation you have with your vet. Convenia is a good drug in the right animal for the right infection. It's a poor default.
Key Takeaways
Call us right away if your pet develops facial swelling, hives, vomiting, weakness, pale gums, collapse or any trouble breathing in the hours after a Convenia injection. Anaphylaxis is uncommon but it's reported, and it needs treating immediately. Call (519) 896-0532 or see our emergency information.
Convenia is the brand name for cefovecin, an antibiotic in the cephalosporin family. Cephalosporins are close relatives of penicillin, and they work the same way: they break down the wall the bacterium needs to hold itself together, and the cell bursts.
Your veterinarian gives it as one injection under the skin at 8 mg/kg, so nothing goes home with you.1
The spectrum is broad but not unlimited. It handles Staphylococcus pseudintermedius and Streptococcus well, keeps fair activity against Gram negatives like E. coli, Klebsiella and Proteus, and covers many anaerobes, the bacteria that thrive in deep wounds and abscesses where there's little oxygen.6 It doesn't touch Pseudomonas, and it won't work against methicillin resistant staph.
"Third generation cephalosporin" sounds like an upgrade and isn't, quite. As Merck puts it, the spectrum of the veterinary third generation drugs shouldn't be considered extended.6 Convenia isn't a stronger antibiotic than the oral options. It's a longer one.
About 14 days of treatment, and up to 65 days in the body. Those are two different numbers and both of them matter.
The 14 days is the treating window. That's the number your vet quotes and the one on the label.
It stays in the body for up to 65 days.1 The half life is 133 hours in dogs and 166 hours in cats, which is roughly five and a half days and seven days, so the drug comes down slowly and keeps coming down long after it has stopped doing useful work.
Most of the time that's harmless. It becomes relevant if your pet has a reaction, because there's no way to discontinue an injection. The label puts it plainly: adverse reactions may need prolonged treatment because of the prolonged clearance.1 With a tablet you stop giving it and the drug is gone in a day or two. With Convenia you're treating the reaction while the drug is still on board.
If the infection hasn't fully resolved at the two week mark, a second injection can be given. The label caps treatment at two injections.1
Skin infections, in both species, and that's only what it is approved for in North America.
| Species | Approved for | Bacteria named on the label |
|---|---|---|
| Dogs | Skin infections: secondary superficial pyoderma, abscesses and wounds | Staphylococcus intermedius (now classified as S. pseudintermedius), Streptococcus canis |
| Cats | Skin infections: wounds and abscesses | Pasteurella multocida |
That's the North American label.1 Urinary tract infections and respiratory infections aren't on it.
Off label prescribing isn't wrong, and I do it most days. Plenty of good veterinary medicine happens off label because the approval process is narrow and the evidence moves faster than the paperwork. But it should be a decision, not an assumption, and the two most common off label uses of this drug are both ones the guidelines push back on.
For urinary infections, the ISCAID guidelines put amoxicillin, amoxicillin-clavulanate and trimethoprim-sulfonamide first, and reserve third generation cephalosporins for cases where those have been shown to be resistant on a culture.4 So Convenia for a straightforward bladder infection skips two safer, cheaper, narrower drugs to get there.
Usually it isn't the right drug, and often no antibiotic is the right answer at all.
Most cats with a snotty nose and sneezing have feline herpesvirus or calicivirus. Those are viruses. An antibiotic does nothing to them. The ISCAID respiratory guidelines say that if the discharge is watery with no pus in it, antibiotics aren't recommended, because a straightforward viral infection is the likely explanation.2
Where an antibiotic earns its place is when there's thick yellow or green discharge and your cat has a fever, is off food, or has gone flat. The working group recommends holding off through a 10 day observation period unless that combination is present.2 A runny nose alone doesn't get there.
When treatment is warranted, doxycycline for 7 to 10 days is the recommended first choice. It's well tolerated, resistance is low, and it covers Bordetella, Chlamydia and Mycoplasma, the three bacteria that actually turn up in these cats.2
Cefovecin was tested directly against this. In a study of shelter cats with suspected bacterial upper respiratory infection, it came out inferior to both doxycycline and amoxicillin-clavulanate, and the ISCAID working group concluded there wasn't enough evidence to recommend it for this use.2
It still gets used because pilling a sick, congested cat twice a day for ten days is hard, and a cat who spits out half the doses gets an incomplete course. Treating that cat with one injection is a reasonable call and I've made it. It just shouldn't be the first thing reached for. Azithromycin is worth discussing too, since the dosing is far less demanding than doxycycline.
Convenia gets chosen for who is holding the pill bottle at 7am, not because it's stronger than the oral options.
The 2025 ISCAID pyoderma guidelines make that explicit for the one use Convenia is actually approved for in dogs. Topical treatment with 2 to 4% chlorhexidine is the treatment of choice for superficial pyoderma, and the guidelines state there are no clinical reasons to use a systemic antibiotic over topical therapy alone. Systemic drugs are indicated based on owner and patient factors, meaning the topical plan isn't going to get done.3
| Option | How it's given | Course | Usual role |
|---|---|---|---|
| Convenia (cefovecin) | One injection at the clinic | ~14 days per injection, max 2 | Skin infections when oral dosing isn't realistic |
| Amoxicillin-clavulanate (Clavamox) | Oral, twice daily | Set by response | First line for many skin and bladder infections |
| Cefalexin | Oral, two to three times daily | Set by response | First line systemic option for canine pyoderma3 |
| Doxycycline | Oral, once to twice daily | 7 to 10 days for feline URI2 | First line for respiratory infections |
| Topical chlorhexidine | Shampoo, mousse or wipes at home | Ongoing | Treatment of choice for superficial pyoderma3 |
Lyme disease is the off label use with the best evidence behind it. Cefovecin has been tested against it in dogs and held up: two injections given 14 days apart produced a sustained drop in joint lesions and circulating antibodies, comparable to 31 days of daily doxycycline or amoxicillin.5 Note the two injections. That's a different protocol from the single shot people picture, and Lyme isn't a labelled indication. If your dog has tested positive after a tick bite, it's a conversation to have rather than an obvious default.
Then there's resistance, which is the reason I'm careful with this drug beyond any individual patient. Leaning on broad spectrum third generation cephalosporins selects for the bacteria that survive them, and those are harder to treat next time. Methicillin resistant staph is the version of that problem I see in practice, and it's a miserable thing to manage. Every unnecessary broad spectrum course makes it slightly more likely. For infections where a narrower drug will do the job, metronidazole and the first generation cephalosporins exist for a reason.
Most pets get one injection and you never notice a thing. The common reactions are mild and they're what you'd expect from an antibiotic.
Vomiting, soft stool or diarrhea, reduced appetite and a quiet day or two are the usual complaints. Some animals are tender at the injection site.
The serious reactions are uncommon, but they're real and I'd rather you knew about them. Post approval reporting for dogs and cats includes death, tremors and incoordination, seizures, anaphylaxis and acute fluid on the lungs.1 That list isn't a reason to refuse the drug. Events reported voluntarily after approval have no denominator behind them, so there's no rate attached, and these outcomes are rare against the number of doses given. It is a reason to take a reaction seriously rather than waiting it out.
Convenia is contraindicated in any dog or cat with a known allergy to cefovecin or to the beta lactam group, which covers penicillins and cephalosporins.1 Tell your vet if your pet has ever reacted to amoxicillin, Clavamox or cefalexin. That history changes the plan.
The 65 day clearance matters most here. An allergic reaction to a tablet resolves as the drug clears, which is quick. With Convenia the drug is still in circulation while you're managing the reaction, so treatment can run longer.1 If you've seen your pet react to a vaccine or an injection before, mention it before this one is given, not after.
Yes. The label names four drugs specifically, and two of them are ones a lot of our patients are already on.
Cefovecin binds tightly to the proteins in blood: 98.5% in dogs and 99.8% in cats.1 Other highly protein bound drugs compete for the same parking spots. When one gets displaced, more of it floats free in the bloodstream, and free drug is active drug. Both medications can effectively be dosed higher than intended without anything changing on the label.
In testing, Convenia raised the free concentration of carprofen, furosemide, doxycycline and ketoconazole.1 It then goes further and warns that other strongly protein bound drugs may do the same, listing NSAIDs generally, propofol, and cardiac, anticonvulsant and behavioural medications.1
Carprofen is on a large share of the arthritic dogs in this practice. Furosemide is on most of the heart patients. These aren't exotic combinations, they're Tuesday.
None of it makes the combination forbidden. It makes it a decision. If your dog is on long term carprofen or furosemide, I'd want to know that before reaching for Convenia, and depending on the case I might pick a different antibiotic or plan on monitoring.
So bring the full list to the appointment. Prescriptions, over the counter products, joint supplements, anything you're adding to food. The interactions here are predictable when we know about them and invisible when we don't.
If your pet has been prescribed Convenia and you're unsure whether it's the right fit, or you want to talk through the alternatives, give us a call at (519) 896-0532. It's a fair question and a short conversation.
Convenia treats for about 14 days, but it stays in the body for up to 65 days. The half life is 133 hours in dogs and 166 hours in cats, so the drug clears slowly long after it has stopped doing useful work. That gap is the reason to think carefully before giving it. There is no way to discontinue an injection, and the label notes that adverse reactions may need prolonged treatment because the drug is still in circulation. If the infection has not fully resolved at two weeks, a second injection can be given. Two is the maximum.
Usually it is not the right choice, and often no antibiotic is. Most cats with sneezing and a runny nose have feline herpesvirus or calicivirus, and antibiotics do nothing to a virus. The ISCAID respiratory guidelines recommend against antibiotics when the discharge is watery with no pus in it. When treatment is warranted, which means thick yellow or green discharge together with fever, lethargy or loss of appetite, doxycycline for 7 to 10 days is the recommended first choice. Cefovecin was tested against this directly in shelter cats and came out inferior to both doxycycline and amoxicillin-clavulanate, and the working group did not recommend it for this use. It still has a place in a cat who cannot be given oral medication at all, because a half finished course of doxycycline helps nobody.
Most pets have no reaction at all. The common side effects are mild: vomiting, soft stool or diarrhea, reduced appetite, a quiet day or two, and tenderness at the injection site. Serious reactions are uncommon but they are reported, and the post approval list for dogs and cats includes death, tremors and incoordination, seizures, anaphylaxis and acute fluid on the lungs. These reports are voluntary and have no rate attached to them, so the events are rare against the number of doses given. Convenia is contraindicated in any dog or cat with a known allergy to cefovecin or to penicillins and cephalosporins, so tell your vet if your pet has ever reacted to amoxicillin, Clavamox or cefalexin.
It can, but your vet should weigh the combination first. Cefovecin is 98.5% protein bound in dogs and 99.8% in cats, so it competes with other highly protein bound drugs for the same binding sites. When one is displaced, more of it circulates freely and both drugs can effectively act as though they were dosed higher. The label names carprofen, furosemide, doxycycline and ketoconazole specifically, and warns that NSAIDs generally, propofol, and cardiac, anticonvulsant and behavioural medications may behave the same way. Carprofen and furosemide are common long term prescriptions, so bring a full list of everything your pet takes, including over the counter products and supplements, to the appointment.
In North America the label covers skin infections only. In dogs that means secondary superficial pyoderma, abscesses and wounds caused by Staphylococcus pseudintermedius and Streptococcus canis. In cats it means wounds and abscesses caused by Pasteurella multocida. Urinary tract infections and respiratory infections are not on the label. Off label use is not automatically wrong and happens routinely in good practice, but for both of those the guidelines point elsewhere first. For bladder infections, ISCAID puts amoxicillin, amoxicillin-clavulanate and trimethoprim-sulfonamide ahead of third generation cephalosporins unless a culture shows resistance.
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