Procaine Penicillin G: veterinary dose and monograph

At a glance

Drug class

Antibiotic

Also known as

Procaine benzylpenicillin, PPG, Fortified procaine penicillin

Species with doses

Dogs, Cats, Cattle, Horses, Goats, Sheep, Pigs, Rabbits and Ferrets

Routes

IM, SC

Last reviewed

1 October 2026

Indications

• Susceptible Gram-positive infections (Streptococcus, Clostridium, Actinomyces, Erysipelas)
• Leptospirosis; blackleg/clostridial disease; foot rot; strangles (Streptococcus equi)
• Wound/soft-tissue and respiratory infections (susceptible organisms)
• Everyday food-animal/equine penicillin therapy (once-daily depot)

Procaine Penicillin G dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

Dogs

• Susceptible infection: UNITS/kg. Plumb’s p.945 (Greene 2006): 20,000–40,000 U/kg IM or SC q12–24h; leptospiraemia 25,000–40,000 U/kg q12–24h for 14 days, then doxycycline for the carrier state (Ross & Rentko). Not in Papich 5e.

Cats

• Soft-tissue / orthopaedic infection: UNITS/kg. Plumb’s p.945 (Greene 2006): soft tissue 20,000 U/kg IM or SC q12h; orthopaedic 20,000–40,000 U/kg IM q8h; Actinomyces 50,000–100,000 U/kg IM/SC q12h.

Cattle

• Susceptible Gram-positive infection: UNITS/kg. Plumb’s p.945: 25,000 U/kg once daily, twice daily for moderately susceptible bacteria (Gunn); 40,000 U/kg IM once daily (Howard); 10,000–20,000 U/kg IM q12–24h (Jenkins); BRD 66,000 U/kg IM/SC once daily with a 20-day slaughter withdrawal (Hjerpe). Label doses are lower (≈6,600 U/kg) and label withdrawals apply only to them — higher extra-label doses need FARAD-extended meat and milk withdrawals. Aspirate before injecting; never IV. Calves, clostridial abomasitis: 10,000–20,000 U/kg PO q12–24h for 1–4 days.

Horses

• Strangles / susceptible infection: UNITS/kg. Plumb’s p.945: 22,000–44,000 U/kg IM q12h (Whittem); strangles 22,000 U/kg IM q12h early in infection (Foreman); foals 22,000–50,000 U/kg IM q12h. Aspirate first — intravascular procaine causes excitement/collapse. Watch for colitis.

Goats

• Susceptible infection (extra-label): UNITS/kg. Plumb’s p.945 (cattle and other ruminants): 10,000–40,000 U/kg IM q12–24h. No goat label — obtain a FARAD withdrawal before slaughter or milk use.

Sheep

• Foot rot / clostridial disease: UNITS/kg. Plumb’s p.945 (cattle and other ruminants): 10,000–40,000 U/kg IM q12–24h. Label withdrawal applies only at the label dose; higher doses need a FARAD withdrawal. Aspirate before injecting.

Pigs

• Erysipelas / susceptible infection: UNITS/kg. Plumb’s p.945: 40,000 U/kg IM once daily (Howard); 6,600 U/kg IM once daily for no more than 4 days (Wood — label dose). Label withdrawal applies only at the label dose; obtain FARAD advice for higher doses.

Buffalo

No buffalo-specific doses are on file, so buffalo are dosed as cattle.

• Susceptible Gram-positive infection: UNITS/kg. Plumb’s p.945: 25,000 U/kg once daily, twice daily for moderately susceptible bacteria (Gunn); 40,000 U/kg IM once daily (Howard); 10,000–20,000 U/kg IM q12–24h (Jenkins); BRD 66,000 U/kg IM/SC once daily with a 20-day slaughter withdrawal (Hjerpe). Label doses are lower (≈6,600 U/kg) and label withdrawals apply only to them — higher extra-label doses need FARAD-extended meat and milk withdrawals. Aspirate before injecting; never IV. Calves, clostridial abomasitis: 10,000–20,000 U/kg PO q12–24h for 1–4 days.

Rabbits

• Venereal spirochetosis (Treponema): UNITS/kg. Plumb’s p.945 (Ivey & Morrisey 2000): 20,000–84,000 U/kg SC or IM q24h. Parenteral only — oral penicillins cause fatal dysbiosis in rabbits.

Ferrets

• Susceptible infection: UNITS/kg. Plumb’s p.945 (Williams 2000): procaine penicillin G 20,000–40,000 units/kg IM once or twice daily.

Contraindications

INTRAVASCULAR / IV injection (fatal procaine reaction — always aspirate; IM only). Penicillin/procaine (local anaesthetic ester) hypersensitivity. NEVER orally in rabbits/guinea pigs/hamsters (fatal enterotoxaemia). Adult horses/hindgut fermenters risk antibiotic-associated colitis. Observe food-animal withdrawal.

Species-specific warnings

Horses: Aspirate carefully — procaine reactions are a well-known equine hazard; also watch for antibiotic-associated colitis and drug-test positives.

Rabbits: Never give penicillins orally to rabbits/small mammals — fatal enterotoxaemia.

Adverse effects

• PROCAINE reaction if given IV/intravascular (excitement, ataxia, collapse, death)
• Hypersensitivity/anaphylaxis (penicillin)
• Injection-site swelling/pain, sterile abscess
• Antibiotic-associated diarrhoea/colitis (horses); positive drug tests (procaine)

Drug interactions

• Aminoglycosides (dihydrostreptomycin): synergy/broader cover (fortified products) — but inactivate each other if mixed and stored
• Bacteriostatic antibiotics: possible antagonism
• Probenecid: prolongs penicillin levels
• Procaine: local-anaesthetic interactions; positive competition drug tests

Pregnancy and lactation

Penicillins are among the safest antibiotics in pregnancy/lactation; widely used in food animals (observe withdrawal).

Monitoring

• Aspirate the syringe before injecting (avoid intravascular procaine reaction) — the key safety step
• Hypersensitivity at first dose; injection-site reactions
• Clinical response; food-animal withdrawal compliance
• Procaine positive drug tests in competition horses

Toxicity and overdose

Two distinct hazards: (1) penicillin hypersensitivity/anaphylaxis, and (2) the PROCAINE reaction from inadvertent intravascular injection — acute CNS excitement, ataxia, tremor, collapse, and occasionally death (procaine toxicity, not penicillin). Very wide margin otherwise. Oral penicillins are fatal to rabbits/small hindgut fermenters.

Management: For a procaine reaction: this is usually self-limiting over minutes — keep the animal calm/safe, provide supportive care; severe cases need cardiovascular/respiratory support. For anaphylaxis: epinephrine 0.01 mg/kg IM, antihistamine, corticosteroid, oxygen, IV fluids. No specific antidote — ALWAYS aspirate before injecting to prevent the reaction.

Clinical pearls

• The everyday once-daily depot penicillin for cattle/horses/pigs — procaine slows release for ~24 h of cover (unlike crystalline penicillin G, which needs frequent dosing)
• ALWAYS aspirate before IM injection — accidental IV delivery causes an acute, sometimes fatal PROCAINE reaction (a distinct hazard from penicillin allergy)
• Shake the suspension and keep it refrigerated; Indian products are often fortified with dihydrostreptomycin for broader cover
• Remember procaine can trigger positive drug tests in performance horses; observe food-animal withdrawal

Mechanism of action

The penicillin-G moiety is a beta-lactam that binds penicillin-binding proteins, inhibiting peptidoglycan cross-linking and bacterial cell-wall synthesis — bactericidal, time-dependent. The procaine salt is poorly soluble, forming a depot at the IM site from which penicillin is released slowly over ~24 h (sustained therapeutic levels from once-daily dosing). Free procaine (a local anaesthetic) released intravascularly is responsible for the acute CNS "procaine reaction."

Formulations and products

• Injectable suspension 300,000 IU/mL
• Fortified procaine penicillin (with dihydrostreptomycin)
• Procaine Penicillin (± dihydrostreptomycin) (Various (India)) — 300,000 IU/mL suspension (fortified forms), IM depot injection
• Strepto-Penicillin 2.5 g (Assure Biotech, Jagadhri (HR)) — Procaine penicillin G 1.5 MIU + Penicillin G sodium 0.5 MIU + Streptomycin base 2.5 g, Dry powder vial for suspension
• Strepto-Penicillin 5 g (Assure Biotech, Jagadhri (HR)) — Procaine penicillin G 3 MIU + Penicillin G sodium 3 MIU + Streptomycin base 5 g, Dry powder vial for suspension

Storage

Suspension: REFRIGERATE (2–8 °C) per label; shake well before use (settles). Do not freeze. Protect from light.

Before you use this dose

Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

Other antibiotics

• Penicillin G
• Pirlimycin
• Polymyxin B
• Pradofloxacin
• Rifampin
• Rifaximin
• Silver Sulfadiazine
• Spectinomycin

Frequently asked questions