Penicillin G Benzathine/Procaine for Rabbits: Uses, Dosing & Side Effects

This information is for educational purposes only. Never give your pet any medication without your veterinarian's guidance. Dosing, frequency, and safety depend on your pet's specific health profile.

Penicillin G benzathine/procaine is a long-acting injectable antibiotic combination. Both ingredients are forms of penicillin G, but they release at different speeds after an injection. In rabbit medicine, your vet may use it extra-label for carefully selected bacterial infections, especially when the suspected bacteria are likely to respond and the route of administration is safe.

The biggest safety point is route. Oral penicillin can be dangerous or even fatal in rabbits because it can disrupt normal gut bacteria and trigger severe dysbiosis, diarrhea, dehydration, and enterotoxemia. That is why rabbit treatment plans use this medication as an injection only, not by mouth.

This drug is not a good fit for every infection. Rabbits commonly develop mixed infections, deep abscesses, or infections linked to dental disease, and many cases need culture, imaging, flushing, surgery, pain control, assisted feeding, or all of the above. Penicillin can be one tool in that larger plan, but it is rarely the whole plan by itself.

Rabbit-savvy vets most often consider penicillin G benzathine/procaine for susceptible bacterial infections such as some abscesses, skin and soft tissue infections, wound infections, and certain dental-related infections. It has also been used in rabbits with Treponema cuniculi infection and in some chronic upper respiratory infections when exam findings and testing support that choice.

In practice, this medication is often discussed for rabbits with the thick, caseous pus seen in abscess disease. Those cases can be frustrating because the infection may be walled off, involve bone or tooth roots, or return after drainage alone. Your vet may pair penicillin injections with abscess debridement, tooth work, culture and susceptibility testing, pain medication, and nutrition support.

It is not effective against every organism, and it may not penetrate every infected area well enough on its own. That is why your vet may recommend culture results, skull imaging, or a recheck plan before deciding whether penicillin is the right option, whether another antibiotic makes more sense, or whether surgery needs to be part of treatment.

See your vet immediately if your rabbit has stopped eating, has diarrhea, seems bloated, is struggling to breathe, or has a rapidly enlarging abscess. Rabbits can decline quickly, and antibiotic decisions should be based on the rabbit's exam, hydration status, gut function, and likely infection source.

For rabbits, penicillin G benzathine/procaine is typically given by subcutaneous or intramuscular injection under veterinary direction. Published rabbit references describe regimens such as 40,000 IU/kg subcutaneously every 24 hours for 2 weeks, then every 48 hours for 2 or more weeks for some pasteurellosis cases, while other formularies list combination penicillin G benzathine/procaine around 42,000 to 84,000 IU/kg every 3 to 7 days depending on the condition and formulation. Exact dose, route, interval, and duration vary with the infection site, product concentration, kidney function, and whether your rabbit is improving.

Because commercial products come in different concentrations and are easy to mis-measure, pet parents should never calculate or substitute doses on their own. Your vet may also show you how to warm the syringe in your hand, rotate injection sites, and monitor appetite and stool output at home. If a dose is missed, given late, or partially spilled, call your vet before repeating it.

The most important side effects to watch for are reduced appetite, smaller or fewer fecal pellets, diarrhea, lethargy, worsening pain, or swelling at the injection site. Even though injectable penicillin is much safer than oral penicillin in rabbits, any antibiotic can still affect gut health. A rabbit that eats less for even part of a day may need prompt reassessment.

Some rabbits develop injection-site soreness, a small lump, or local irritation. Mild discomfort can happen with thick, long-acting suspensions. More serious concerns include marked swelling, heat, discharge, or skin damage where the medication was given.

Allergic reactions are uncommon but possible with penicillins. Call your vet right away if you notice facial swelling, hives, sudden weakness, collapse, or breathing changes after an injection. Because this product contains procaine, accidental injection into a blood vessel is also a safety concern and can cause acute neurologic signs. That is one reason your vet may prefer to give the first dose in clinic or carefully teach home injection technique.

Penicillin G can interact with other medications, so your vet should review every prescription, supplement, probiotic, and pain medication your rabbit receives. One classic interaction is with probenecid, which can reduce renal excretion of penicillin and raise penicillin levels in the body. That combination is uncommon in rabbits, but it matters if your rabbit is medically complex.

Your vet will also think about the bigger clinical picture rather than a single textbook interaction. For example, combining antibiotics may be reasonable in some abscess cases, but it can also increase the risk of appetite loss or gut upset. Rabbits with dehydration, kidney disease, severe GI slowdown, or a history of antibiotic-associated dysbiosis may need a different plan or closer monitoring.

Tell your vet if your rabbit has ever had a reaction to penicillin or cephalosporin antibiotics. Because rabbits are so sensitive to changes in intestinal flora, never add over-the-counter human antibiotics, leftover pet medications, or oral penicillin-family drugs unless your vet specifically instructs you to do so.