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Pharmaceuticals2026-05-16 · 9 min read

Convenia Injection for Dogs and Cats: What Cefovecin Treats, How Long It Lasts

An evidence-based guide to Convenia (cefovecin) for dogs and cats: what infections it treats, how long the drug stays in the body, adverse event risks, and when oral antibiotics are safer.

Ran Chen
Ran Chen
Founder, VetMedGuide. Life-sciences operator and 10× global market-access lead.
Published

Convenia (cefovecin sodium) is the only FDA-approved long-acting injectable antibiotic available for dogs and cats. A single subcutaneous injection provides therapeutic antibiotic levels for approximately 14 days, which makes it useful when daily pilling is impractical or impossible.

That convenience is real, but so is the concern. Because cefovecin takes roughly 65 days to clear 97% of the administered dose from the body, any adverse reaction that occurs after injection cannot be reversed by stopping the drug — there is no "off switch." This article covers what the label approves, how cefovecin works, what the adverse-event data shows, and when a veterinarian and owner might choose a different antibiotic.

What Convenia is

Cefovecin is a third-generation cephalosporin. It kills bacteria by interfering with cell wall synthesis, and it is active against many gram-positive and some gram-negative organisms. Zoetis manufactures the branded product; generics including Solovecin (Dechra; launched November 2025) and Cefovecin Sodium for Injection (Qilu Animal Health Products; FDA-approved June 2025) have entered the US market.

After subcutaneous injection, cefovecin binds extensively to plasma proteins — primarily albumin — and is released slowly. This protein binding is what creates the long duration of therapeutic levels. The drug is excreted largely unchanged via the kidneys.

What the FDA label covers

Dogs

Convenia is FDA-approved in dogs for the treatment of:

  • Superficial pyoderma (bacterial skin infections)
  • Wounds and abscesses caused by susceptible strains of Staphylococcus intermedius and Streptococcus canis (Group G)

A single injection provides 14 days of therapy. For dogs that have not fully responded after 14 days, the label allows a second injection.

Cats

Convenia is FDA-approved in cats for the treatment of:

  • Skin infections including wounds and abscesses caused by susceptible strains of Pasteurella multocida

In the European Union, United Kingdom, and Australia, Convenia also carries approved indications for urinary tract infections in cats. In the US, cefovecin is used off-label for UTIs based on culture and susceptibility results, but this is not an FDA-approved indication.

One injection is generally sufficient in cats. The label does not call for a second dose.

How quickly it works and how long it stays

Cefovecin reaches therapeutic plasma concentrations quickly — within approximately 2 hours in cats and 6 hours in dogs — and begins killing susceptible bacteria. Clinical improvement is often visible within 24–48 hours, though the full course of antibacterial activity continues for up to 14 days.

What makes cefovecin unusual among veterinary antibiotics is its persistence. According to the Zoetis label, approximately 65 days are needed to eliminate 97% of the administered dose. Trace amounts remain detectable well beyond the 14-day therapeutic window. This long tail is a pharmacokinetic feature that creates the drug's main clinical limitation: if a dog or cat develops an adverse reaction, the drug cannot be removed from the body faster than its natural clearance rate. Supportive care is the only option.

When the long duration helps

Convenia is most useful in situations where daily oral medication is genuinely not feasible:

  • Aggressive or fractious cats that cannot be safely pilled at home
  • Stray or feral cats receiving one-time veterinary care with no follow-up owner compliance
  • Owners with physical limitations who cannot administer pills
  • Shelter animals where daily individual medication is logistically impractical
  • Injection-site abscesses or bite wounds where a single-visit treatment ensures the full course is completed

In these situations, the certainty of a completed antibiotic course can outweigh the downside of an injection that cannot be reversed.

When Convenia is not the right choice

The label contraindicates cefovecin in animals with a known allergy to cephalosporins or penicillins. Anaphylaxis has been reported, and because the drug persists for months, any allergic response may be prolonged.

Beyond the formal contraindication, there are clinical situations where the risks of an irreversible long-acting antibiotic outweigh the convenience:

No culture and sensitivity data

Convenia is a cephalosporin with a specific spectrum. If the infection is caused by bacteria resistant to cephalosporins — including many Pseudomonas, Enterococcus, and MRSA isolates — the injection provides no benefit while still carrying risk. For deep infections, chronic or recurrent infections, or cases that have already failed antibiotics, culture and susceptibility testing should guide drug selection before reaching for a long-acting injectable that cannot be adjusted.

Medically fragile patients

Because adverse reactions cannot be reversed, veterinarians and owners should be cautious with geriatric patients, animals with known organ dysfunction, or patients already on multiple medications. The label states that safe use has not been evaluated in animals younger than 4 months, or in breeding, pregnant, or lactating animals.

When antibiotic stewardship matters

Long-acting broad-spectrum antibiotics exert selection pressure for an extended period. Cornell University's College of Veterinary Medicine has an active research program studying whether cefovecin use in cats drives antimicrobial resistance in commensal bacteria, noting that the drug's long half-life exposes gut flora to sub-inhibitory concentrations for weeks. In an era of increasing antimicrobial resistance, reserving cefovecin for cases where oral therapy truly is not feasible — rather than using it for convenience alone — is consistent with responsible prescribing practices outlined by the AVMA and FDA CVM.

Adverse events: what the data shows

The label and post-marketing experience identify several categories of adverse events:

Common side effects

Vomiting, diarrhea, lethargy, and decreased appetite are the most frequently reported. These are similar in frequency to other antibiotics and are generally mild. However, because the drug takes 65 days to clear, even common side effects can be prolonged — Today's Veterinary Practice has reported that diarrhea has been documented to last up to 28 days in dogs and 42 days in cats following a single injection.

Allergic and anaphylactic reactions

The label warns that anaphylaxis has been reported. Because the drug persists in the body for months, allergic reactions may be prolonged and require sustained supportive care, including epinephrine, antihistamines, corticosteroids, IV fluids, and oxygen as clinically indicated. Animals that experience an allergic reaction should never receive cefovecin again.

Severe adverse events

Post-marketing reports have documented severe reactions including immune-mediated hemolytic anemia (IMHA), acute renal failure, and death. Today's Veterinary Practice has also noted reports of cephalosporin-associated myelotoxicity leading to toxic neutropenia, anemia, and death in dogs and cats. These reports are the basis for the ongoing controversy surrounding Convenia. A Change.org petition and multiple Facebook groups have collected owner reports of adverse outcomes.

Dr. Lisa Pierson, a veterinarian who has written extensively about cefovecin safety at catinfo.org, advises that Convenia should not be used as a first-line antibiotic in cats when oral alternatives exist. Her position is that the long drug clearance time makes adverse reactions uniquely dangerous compared to drugs that can be stopped and cleared quickly.

It is important to note that post-marketing reports do not establish causation. The rate of severe adverse events relative to the total number of doses administered is not publicly available in a way that allows comparison to other antibiotics. What is clear is that when a severe reaction does occur, the inability to stop the drug makes the situation harder to manage.

Convenia vs oral antibiotics: practical comparison

Factor Convenia (cefovecin) Oral antibiotics (e.g., amoxicillin-clavulanate)
Administration Single SC injection at veterinary clinic Daily oral doses at home for 7–14 days
Compliance Guaranteed (given by vet) Depends on owner ability to pill
Duration of drug activity 14 days therapeutic; ~65 days to clear 97% Hours per dose; clears within 1–2 days of last dose
Can be stopped? No Yes
Cost per course $50–100 per injection $15–40 for full oral course
Spectrum Cephalosporin range (gram-positive + some gram-negative) Varies by drug; can be tailored to culture results
Monitoring for reactions Extended (weeks to months) Standard (days)
Best for Difficult-to-pill animals, single-visit scenarios Most routine infections where compliance is possible

What to ask your veterinarian

If a veterinarian recommends Convenia, the following questions can help clarify whether it is the best option for the specific situation:

  • Was a culture and sensitivity performed? If not, ask whether the infection is likely to respond to a cephalosporin based on the suspected organism.
  • Is oral medication truly not feasible? If the reason is difficulty pilling, ask about compounding flavored liquids, transdermal options for certain drugs, or pill-hiding treats.
  • What are the monitoring expectations? Because the drug persists, ask what signs to watch for and when to return if the pet is not improving.
  • Is this the pet's first antibiotic for this issue? If the pet has already failed a prior course, culture-guided therapy is more appropriate than a long-acting injectable with a fixed spectrum.

Sources

Topics
Antibiotics & Anti-Infectives
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