Vetrimoxin L.A. for Cattle & Pigs: Complete Guide – How Long-Acting Amoxicillin Works, Full Dosage by Weight, Withdrawal Periods & FAQs on Sheep, Dogs & Cats
Vetrimoxin L.A. is Ceva Animal Health’s long-acting amoxicillin injectable for cattle and pigs. Unlike standard amoxicillin injections that require once-daily treatment, Vetrimoxin L.A.’s depot formulation maintains therapeutic concentrations for 48 hours per injection, halving the handling required per treatment course. This guide covers everything: what “long-acting” actually means at the pharmacokinetic level, dosage by body weight with worked examples, withdrawal periods, and the frequently asked questions about use in sheep, dogs, and cats.
What Does “Long-Acting” Mean for an Amoxicillin Injection?
Standard amoxicillin injections use amoxicillin trihydrate dissolved in an aqueous vehicle. After intramuscular injection, the drug is absorbed rapidly — peak plasma concentrations are reached within 1–2 hours, and the drug is cleared within 12–24 hours. To maintain therapeutic concentrations, once-daily dosing is required.
Vetrimoxin L.A. uses micronized amoxicillin trihydrate in a suspension vehicle. Rather than dissolving and absorbing immediately, the fine amoxicillin particles form a depot at the injection site. The drug is then absorbed slowly from this depot over the following 48 hours, maintaining effective blood concentrations throughout. A single injection on Day 1 and a second on Day 3 (48 hours later) constitutes a complete treatment course.
The micronization serves a second purpose: smaller particle size means the suspension passes smoothly through needles of all gauges, including the finer needles used in pigs where thick suspensions can be difficult to inject.
How Amoxicillin Works — And Why Bacteriostatic Drugs Must Not Be Combined
Amoxicillin is a bactericidal antibiotic of the aminopenicillin class. It kills bacteria by inhibiting penicillin-binding proteins (PBPs) — the transpeptidase enzymes responsible for cross-linking the peptidoglycan strands that form the bacterial cell wall. Without this cross-linking, the cell wall cannot be maintained, and the bacterium ruptures under its own internal osmotic pressure during cell division.
This mechanism has a critical clinical implication: amoxicillin is only lethal to bacteria that are actively dividing. The cross-linking it inhibits happens during cell wall synthesis — a process that only occurs when bacteria are growing and replicating. This explains why combining amoxicillin with bacteriostatic antibiotics is counterproductive and contraindicated:
- Tetracyclines (oxytetracycline) — inhibit bacterial protein synthesis and arrest growth; bacteria stop dividing and amoxicillin has no target
- Macrolides (tylosin, tulathromycin, tilmicosin) — also bacteriostatic protein synthesis inhibitors; same antagonism
- Sulphonamides — bacteriostatic at clinical doses
- Chloramphenicol / florfenicol — bacteriostatic
In practice: if you’re treating Bovine Respiratory Disease with both an amoxicillin product and a macrolide or tetracycline, they should not be given simultaneously. Discuss timing and drug selection with your veterinarian.
Indications: Bovine Respiratory Disease and Swine Respiratory Infections
Bovine Respiratory Disease (BRD) in Cattle
BRD is the most economically damaging bacterial disease in cattle production, costing the global industry billions annually in mortality, reduced performance, and treatment costs. The disease typically follows a viral respiratory insult (IBR, BVD, BRSV, PI-3) that compromises the mucociliary clearance of the respiratory tract, allowing secondary bacterial pathogens to establish infection in the lungs.
The two primary bacterial pathogens targeted by Vetrimoxin L.A. in cattle are:
- Mannheimia haemolytica — the dominant bacterial cause of acute BRD fibrinous pneumonia; produces a leucotoxin that damages bovine alveolar macrophages, dramatically impairing pulmonary immune defence. Responsible for the characteristic acute pleuropneumonia with fibrin plaques in feedlot and stressed cattle.
- Pasteurella multocida — associated with a more chronic, subacute form of BRD; frequently found in combination with M. haemolytica in mixed infections and as a secondary coloniser following viral damage.
Clinical signs of BRD include: nasal and ocular discharge, raised respiratory rate, laboured breathing, fever (>39.5°C / 103°F), depression, reduced feed intake, and in acute cases, sudden death. Treatment outcomes are significantly better when antibiotics are initiated early — before lung pathology becomes irreversible. Animals that survive prolonged BRD often have permanent lung damage that reduces finishing performance.
Swine Respiratory Infections
In pigs, Vetrimoxin L.A. targets respiratory infections caused by Pasteurella multocida, a key pathogen in the swine respiratory disease complex. Clinical signs include coughing, dyspnoea, reduced growth rates, and fever. As in cattle, early treatment gives the best outcomes.
Complete Dosage Guide
Dose: 1ml per 10kg body weight (= 15mg amoxicillin per kg). Administered by deep intramuscular injection. Shake the vial vigorously before each dose.
Dosing Schedule
| Day | Action |
|---|---|
| Day 1 | First injection at 1ml/10kg IM |
| Day 3 (48 hours later) | Second injection at 1ml/10kg IM, fresh site |
| Day 4–5 | Reassess clinical response. If no improvement, re-evaluate diagnosis. |
Body Weight Dosage Table
| Animal | Weight | Volume per Dose | Sites Needed |
|---|---|---|---|
| Calf | 50 kg | 5 ml | 1 (under 20ml cattle limit) |
| Calf | 100 kg | 10 ml | 1 |
| Beef steer | 300 kg | 30 ml | 2 sites × 15ml |
| Beef steer | 400 kg | 40 ml | 2 sites × 20ml |
| Dairy cow | 600 kg | 60 ml | 3 sites × 20ml |
| Growing pig | 40 kg | 4 ml | 1 (under 6ml pig limit) |
| Growing pig | 80 kg | 8 ml | 2 sites (max 6ml/site) |
| Sow | 180 kg | 18 ml | 3 sites × 6ml |
100ml Vial Duration
| Animal | Weight | Volume per 2-dose course | Courses from 100ml |
|---|---|---|---|
| Calf | 50 kg | 10 ml total | 10 courses |
| Beef steer | 300 kg | 60 ml total | 1.6 courses |
| Pig | 60 kg | 12 ml total | ~8 courses |
Withdrawal Periods
Do not slaughter or use milk before these periods have elapsed after the last injection:
| Species | Product | Withdrawal |
|---|---|---|
| Cattle | Meat and offal | 18 days |
| Cattle | Milk | 72 hours (3 days / 4 milkings) |
| Pigs | Meat and offal | 20 days |
Always verify against the specific product label in your country — withdrawal periods can vary by regional marketing authorisation.
Vetrimoxin L.A. for Sheep — Is It Appropriate?
This is one of the most searched questions about Vetrimoxin L.A. The licensed indications are cattle and pigs only. However, amoxicillin injectable products at 150mg/ml are widely used in sheep under veterinary supervision on an off-label basis for:
- Respiratory disease (Mannheimia haemolytica, Pasteurella multocida — same organisms as bovine BRD)
- Foot rot and foot abscess
- Neonatal infections (joint ill, naval ill in lambs)
- Mastitis
The standard off-label dose is the same: 1ml per 10kg (15mg/kg) every 48 hours. Extended withdrawal periods apply for off-label use in sheep — consult your veterinarian for the appropriate withdrawal to declare. Off-label use should always be under veterinary supervision.
Vetrimoxin L.A. for Dogs or Cats — Why It’s Not Appropriate
Both “vetrimoxin for dogs” and “vetrimoxin for cats” are genuinely searched queries, so this is worth addressing clearly.
Vetrimoxin L.A. is a livestock injectable formulation. It is not licensed for dogs or cats, and its use in companion animals is not appropriate for several practical reasons:
- The 150mg/ml concentration and large vial sizes (100ml+) are designed for livestock bodyweights. Accurate dosing for a 5kg cat (requiring 0.5ml) from a large shared multi-use vial is practically difficult.
- Dogs and cats do use amoxicillin therapeutically, but through oral amoxicillin-clavulanate tablets (Clavaseptin, Synulox) or dedicated small-animal injectable formulations with appropriate veterinary prescribing.
- The 28-day open-vial stability means a large livestock vial opened for a single small animal dose would waste significant product.
If your dog or cat needs amoxicillin treatment, the appropriate products are veterinary-licensed small animal formulations prescribed by your vet.
Critical Reminders for Vetrimoxin L.A. Use
- Shake vigorously before every dose — the suspension settles; inadequate mixing causes inaccurate dosing
- Maximum 10 needle penetrations per vial — to preserve sterility; use automatic syringes for herd treatments
- Do not mix with other antibiotics in the same syringe
- Do not use concurrently with tetracyclines, macrolides, sulphonamides, or chloramphenicol — bacteriostatic antagonism
- Weigh animals accurately — underdosing risks treatment failure and resistance development
- Reassess after the second dose — if no improvement, change treatment rather than continuing amoxicillin
Where to Buy Vetrimoxin L.A.
You can order Vetrimoxin L.A. (Amoxicillin 150mg/ml) 100ml from PetShopBoss.com with free worldwide shipping.
Related: Dufamox 15% L.A. – Alternative long-acting amoxicillin injectable | Shotapen LA (Benzylpenicillin + Dihydrostreptomycin) – broad-spectrum dual antibiotic for cattle
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