A single Convenia injection provides therapeutic antibiotic levels for 7 to 14 days, depending on the type of infection and whether your pet is a cat or a dog. After the active treatment window closes, trace amounts of the drug can linger in your pet’s body for up to 65 days before being fully cleared.
Therapeutic Duration in Dogs vs. Cats
Convenia (the brand name for cefovecin sodium) is a long-acting antibiotic given as a single injection under the skin. It’s FDA-approved to treat skin infections, including wounds, abscesses, and superficial bacterial skin disease. How long it actively fights infection depends on the species and the bacteria involved.
In dogs, therapeutic drug concentrations last 7 days against Staphylococcus intermedius infections and 14 days against Streptococcus canis infections. In cats, the drug maintains effective levels for approximately 7 days against Pasteurella multocida, the bacterium most commonly found in cat bite wounds and abscesses.
These windows represent the period during which the drug is concentrated enough to kill the target bacteria. Outside of this window the antibiotic is still present, but at levels too low to reliably treat an active infection.
How Long Convenia Stays in the Body
The reason Convenia works so differently from a typical oral antibiotic is that it binds tightly to proteins in your pet’s bloodstream, which slows its elimination dramatically. The half-life (the time it takes for the drug concentration to drop by half) is 6.9 days in cats and 5.5 days in dogs. For comparison, most oral antibiotics have half-lives measured in hours, not days.
After the therapeutic window ends, the drug doesn’t vanish. It continues declining in concentration and can exist in small amounts for up to 65 days. This is worth knowing because if your pet has a side effect, you can’t simply stop giving the medication the way you would with pills. The drug is already in the system and will clear on its own timeline.
What Convenia Treats
Convenia has a narrow set of FDA-approved uses. In dogs, it’s indicated for secondary superficial pyoderma (bacterial skin infections that develop on top of an underlying skin problem), abscesses, and wounds caused by specific susceptible bacteria. In cats, it’s approved for wounds and abscesses caused by Pasteurella multocida. Veterinarians sometimes prescribe it off-label for other bacterial infections, particularly in cats that are difficult to medicate orally, but the labeled indications are limited to skin infections.
Re-dosing and Maximum Treatment
Cats receive a single injection only, with no repeat dose approved. Dogs can receive a second injection if the infection hasn’t fully resolved after the first, but the maximum treatment is capped at two injections total. Each dose is 3.6 mg per pound of body weight, given under the skin.
Your vet will decide whether a second dose is warranted based on how the infection looks at a follow-up visit. If two injections don’t clear things up, a different antibiotic or a deeper investigation into the underlying cause is the typical next step.
Side Effects
Convenia is well tolerated in the vast majority of pets. The most commonly reported side effects are digestive issues: vomiting, diarrhea, and loss of appetite. These occur on a “very rare” basis, defined as fewer than 1 in 10,000 animals treated. Neurological signs like loss of coordination or seizures, injection site reactions, and allergic reactions (including severe anaphylaxis) have also been reported at the same very rare frequency.
The key consideration with side effects is the persistence factor. Because the drug stays in the body for weeks, any adverse reaction can’t be shortened by discontinuing treatment. This is one reason veterinarians weigh the decision to use Convenia carefully, especially in pets with a history of allergies to penicillin or cephalosporin antibiotics, which are in the same drug family. Convenia is also not approved for use in puppies or kittens under 8 weeks old, or in small herbivores like rabbits and guinea pigs.
Why Vets Choose Convenia
The primary advantage of Convenia is compliance. Anyone who has tried to give a cat oral antibiotics twice a day for two weeks understands the appeal of a single injection that handles the entire course of treatment. For feral or semi-feral cats, for pets that refuse pills, or for owners who struggle with medication schedules, one visit to the vet replaces 14 to 28 individual doses at home. The tradeoff is that once it’s injected, you’re committed to the full course with no option to stop early if problems arise.