Procaine Penicillin G for Cow: 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.

Procaine penicillin G is an injectable penicillin antibiotic used in cattle under your vet's direction. It is a long-acting suspension form of penicillin G, which means the drug is absorbed more slowly than water-soluble penicillin salts and can keep working for longer after an injection. In cattle, it is commonly given by intramuscular injection, and some veterinary references also describe subcutaneous use in specific situations directed by your vet.

This medication works best against penicillin-susceptible bacteria, especially many gram-positive organisms and some anaerobes. It is not the right choice for every infection. Many cattle respiratory cases, foot problems, or uterine infections can involve bacteria that are not reliably covered by penicillin alone, so culture results, herd history, and the cow's clinical condition matter.

Because cattle are food animals, procaine penicillin G also comes with important residue and withdrawal rules. Label directions for one common US product list a milk withdrawal of 48 hours and a slaughter withdrawal of 14 days, with a warning not to use it in calves to be processed for veal. If your vet uses the drug extra-label, withdrawal times may need to be longer.

On US cattle labels, procaine penicillin G is approved for bacterial pneumonia or shipping fever caused by susceptible organisms. In practice, your vet may also consider it for other infections when the likely bacteria are penicillin-sensitive and when food-animal regulations allow that use under a valid veterinary-client-patient relationship.

Examples your vet may discuss include certain wound infections, navel infections, metritis, pyelonephritis, necrotic laryngitis, or necrobacillosis-related infections. That does not mean it is the best fit for every case. Some common cattle pathogens, including organisms involved in bovine respiratory disease, may respond better to other antibiotics depending on severity, resistance patterns, and whether the case is individual or herd-based.

This is why procaine penicillin G should be viewed as one option, not the only option. Your vet may choose it because it is familiar, accessible, and effective for the suspected bacteria, or may recommend a different antimicrobial, supportive care, diagnostics, or a combination plan instead.

Always use procaine penicillin G exactly as your vet prescribes. Dosing in cattle varies depending on the product label, the disease being treated, the route, and whether your vet is using the drug on-label or extra-label. A common labeled concentration is 300,000 units/mL. One FDA-listed cattle label directs 3,000 units per pound of body weight, which equals about 6,600 units/kg, or 1 mL per 100 lb, given intramuscularly once daily for 2 to 4 days. That same label says not to inject more than 10 mL per site and to rotate sites.

Veterinary references often list higher clinical dosing ranges for cattle, such as 22,000 to 66,000 units/kg every 24 hours, but Merck notes that doses above 6,600 units/kg/day are extra-label drug use in cattle. In food animals, extra-label antimicrobial use has legal and residue implications, so your vet must decide whether it is appropriate and what withdrawal interval is needed.

Technique matters. Shake the bottle well, use clean equipment, and follow your vet's instructions for needle size, route, and injection location. Beef Quality Assurance guidance recommends giving injections in the neck, in front of the shoulder, to reduce tissue damage in valuable meat cuts. If a cow is not improving within 24 to 48 hours, contact your vet rather than increasing the dose on your own.

Many cattle tolerate procaine penicillin G well, but side effects can happen. The most common concerns are injection-site pain, swelling, and local tissue reactions. In food animals, these reactions can persist and may matter for carcass quality as well as comfort.

More serious reactions are less common but important. Allergic or anaphylactic reactions can occur unpredictably and may be life-threatening. Signs can include sudden breathing trouble, collapse, severe weakness, facial swelling, or hives. See your vet immediately if any of these happen after an injection.

Other possible problems include lack of response, which may mean the bacteria are not susceptible, and overgrowth of nonsusceptible organisms, including fungi, after antibiotic use. If the cow develops new signs, worsens, stops eating, spikes a fever, or fails to improve after a day or two, your vet may want to reassess the diagnosis, run tests, or switch treatment.

The best-known interaction concern is with bacteriostatic antibiotics, especially tetracyclines. Product labeling advises avoiding concurrent use because tetracyclines may antagonize the bactericidal effect of penicillin. In plain language, one drug can make the other work less effectively.

That does not mean combinations are never used in cattle medicine, but it does mean your vet should make that decision intentionally. Be sure to tell your vet about all recent medications, including oxytetracycline, florfenicol, sulfas, anti-inflammatories, calcium products, and any intramammary or uterine treatments.

Also mention if the cow has had a previous reaction to penicillin or procaine-containing products. In food animals, interaction questions are not only about safety. They can also affect withdrawal planning, residue avoidance, and treatment records, which are essential for both dairy and beef operations.