Penicillin G Procaine for Pigs: 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 procaine is an injectable antibiotic in the penicillin family. In pigs, it is used against certain susceptible bacteria, especially gram-positive organisms. The procaine portion slows absorption after an intramuscular injection, which helps the drug last longer than plain penicillin G.

For swine, labeled products in the US are commonly 300,000 units per mL and are given by intramuscular injection. One FDA-listed swine indication is erysipelas caused by Erysipelothrix rhusiopathiae. Your vet may also consider it in other situations when exam findings, testing, and food-animal regulations support that choice.

Because pigs are food animals, this medication has extra safety rules. Route, dose, duration, and withdrawal times matter. That is why pet parents should never start, stop, or adjust penicillin G procaine without guidance from your vet.

In pigs, penicillin G procaine is most clearly used for swine erysipelas, a bacterial disease that can cause fever, lameness, skin lesions, and sudden illness. When the infecting bacteria are susceptible, penicillin can be a practical first-line option because it is familiar, widely available, and relatively affordable.

Your vet may also weigh penicillin G procaine for other likely penicillin-sensitive infections, such as some skin, soft tissue, joint, or wound infections. That decision should be based on the pig's age, clinical signs, herd or household setting, prior antibiotic exposure, and whether culture and susceptibility testing are needed.

This drug is not a good fit for every infection. Many respiratory and enteric diseases in pigs involve bacteria that may not respond well, mixed infections, or non-bacterial causes. If a pig is severely ill, not eating, struggling to breathe, or worsening despite treatment, see your vet immediately.

Dosing must come from your vet. A commonly cited labeled swine dose for penicillin G procaine injectable suspension is 3,000 units per pound of body weight once daily, which equals 1 mL per 100 lb of a 300,000 units/mL product, given intramuscularly. Labeled treatment is usually continued until recovery is apparent and for at least one day after signs improve, with a maximum of 4 consecutive days on that label.

Veterinary references also list broader swine dosing ranges for procaine penicillin G, roughly 15,000-40,000 units/kg IM every 24 hours, but those uses may be extra-label and require your vet to make the decision. In food animals, extra-label drug use has legal and withdrawal-time implications, so pet parents should not calculate a higher or different dose on their own.

The vial should be brought to room temperature and shaken well to create a uniform suspension before use. Penicillin G procaine is intended for intramuscular use, and careful injection technique matters because accidental injection into the wrong location can damage tissue or nerves. If you are giving injections at home, ask your vet to show you the exact needle size, site, volume per site, and how to rotate sites safely.

For pigs intended for the food chain, withdrawal times are essential. A commonly cited swine slaughter withdrawal period for labeled penicillin G procaine products is 6 days, but your vet may require a longer interval if the use is extra-label.

Many pigs tolerate penicillin G procaine well when it is used correctly, but side effects can happen. The more common problems are injection-site pain, swelling, or irritation. Some animals also develop digestive upset such as reduced appetite, loose stool, or vomiting, although vomiting is less commonly reported in pigs than in dogs or cats.

The most important serious risk is an allergic or hypersensitivity reaction. Watch for facial swelling, hives, sudden weakness, trouble breathing, collapse, or a pig that seems dramatically worse soon after the injection. See your vet immediately if any of those signs appear.

Repeated exposure can sometimes trigger sensitivity even if earlier doses were tolerated. Overdose, wrong-route administration, or poor injection technique can also increase the risk of tissue injury. If your pig seems painful after the shot, develops a large lump, becomes lame, or stops eating, contact your vet promptly.

Penicillin G procaine can interact with other medications, so your vet should review everything your pig is receiving, including antibiotics, anti-inflammatories, supplements, and medicated feed or water products. This is especially important in pigs because treatment plans also have to fit food-animal residue rules.

As a beta-lactam antibiotic, penicillin is generally bactericidal. In some situations, combining bactericidal drugs like penicillins with bacteriostatic antibiotics such as tetracyclines, macrolides, or phenicols may reduce effectiveness, depending on the infection and timing. That does not mean combinations are never used, but it does mean they should be chosen thoughtfully by your vet.

There can also be practical interactions around kidney function, dehydration, and concurrent illness, because sick pigs may handle drugs differently. If your pig is already on another antibiotic and is not improving, do not stack medications at home. Ask your vet whether culture and susceptibility testing, a drug change, or supportive care would make more sense.