Penicillin G Procaine for Sheep: 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 used in sheep to treat infections caused by bacteria that are susceptible to penicillin. It is a beta-lactam antibiotic, which means it works by interfering with bacterial cell wall formation. The procaine part slows absorption, so the drug lasts longer than plain penicillin G after an injection.

In U.S. food animals, this medication now falls under veterinary oversight, so sheep producers should expect to get it through your vet with a valid veterinary-client-patient relationship. That matters because sheep are a food-producing species, and treatment decisions must account for meat and milk withdrawal times, residue avoidance, and whether a planned dose is on-label or extra-label.

Penicillin G procaine is usually given as a deep intramuscular injection in labeled livestock products. The suspension is thick and must be shaken well before use. Because injection technique, site selection, and volume per site affect both comfort and tissue damage, your vet may show you exactly how to give it safely.

In labeled sheep use, penicillin G procaine is commonly associated with treatment of bacterial pneumonia caused by penicillin-susceptible organisms such as Pasteurella multocida. In practice, your vet may also consider it for other infections caused by susceptible bacteria, including some wounds, abscesses, navel infections, foot-related soft tissue infections, and certain reproductive tract infections.

That said, penicillin is not a good fit for every infection. It will not treat viral disease, parasites, or infections caused by resistant bacteria. Some common sheep problems that look infectious at first glance may need a different antibiotic, drainage, anti-inflammatory care, hoof work, culture testing, or supportive care instead.

Because antimicrobial resistance and residue rules matter in sheep, your vet may recommend diagnostics before treatment in higher-value animals, flock outbreaks, repeat infections, or cases that are not improving as expected. Options can range from a practical field exam to culture and sensitivity testing, depending on the situation and your goals.

Always use penicillin G procaine in sheep only under your vet’s direction. Labeled livestock products commonly contain 300,000 units/mL, and the labeled daily dose is 3,000 units per pound of body weight, which equals 1 mL per 100 lb once daily by intramuscular injection. Product labels also warn that exceeding the labeled daily dose, treating for more than 4 consecutive days, or exceeding the maximum volume per injection site can increase the risk of violative residues.

Veterinary references note that clinically used procaine penicillin doses in large animals are often higher than older label doses, which means some sheep treatment plans may be extra-label drug use. In food animals, that decision must come from your vet, who also sets an appropriate withdrawal interval. Do not increase the dose, extend treatment, or switch routes on your own.

Practical dosing details matter. Shake the bottle well, use the needle size your vet recommends, rotate injection sites, and avoid giving a large volume in one spot. If you miss a dose, contact your vet for guidance rather than doubling the next dose. For food safety, keep careful treatment records, including the product used, dose, date, animal ID, and the withdrawal instructions your vet gave you.

Many sheep tolerate penicillin G procaine reasonably well, but side effects can happen. The most common issues are pain, stinging, swelling, or firmness at the injection site. In food animals, labels specifically note that intramuscular injections can cause a local tissue reaction that may persist beyond the labeled withdrawal period.

Digestive upset is also possible, including reduced appetite, loose manure, or diarrhea. Mild signs may pass, but worsening depression, dehydration, or refusal to eat should prompt a call to your vet. Sheep that are already stressed, dehydrated, or dealing with another illness may need closer monitoring.

Rare but serious reactions include allergic or hypersensitivity reactions. Warning signs can include facial swelling, hives, trouble breathing, weakness, collapse, or sudden worsening after an injection. See your vet immediately if any of these occur. Reactions can develop even if an animal seemed fine with earlier doses.

Penicillin G procaine can interact with other medications, so your vet should know everything your sheep has received recently, including antibiotics, anti-inflammatories, dewormers, supplements, and medicated feeds. One important pharmacology point is that penicillins may have synergy with some other antimicrobials, but they can also be a poor match with drugs that are mainly bacteriostatic, because those drugs may reduce the effectiveness of a cell wall-active antibiotic in some situations.

Merck also notes that the procaine portion is metabolized to para-aminobenzoic acid (PABA), which can interfere with sulfonamide antimicrobials. That means combinations are not something to improvise at home. Your vet may also adjust plans in sheep with significant illness, dehydration, or other conditions that change how drugs are tolerated.

For food-producing animals, interaction questions are not only about safety. They also affect withdrawal planning. If your sheep is getting more than one medication, ask your vet which withdrawal interval applies and whether any extra-label use changes the timeline.