Shotapen LA: Complete Dosage Guide for Cattle, Horses, Pigs, Dogs & Cats – Uses, Withdrawal Periods & How It Works
Shotapen LA is a broad-spectrum, long-acting injectable antibiotic manufactured by Virbac. It combines three antibiotics in a single ready-to-use suspension — two forms of benzylpenicillin and dihydrostreptomycin — to deliver both rapid and sustained antibacterial action for up to 72 hours per injection. It is licensed for use across a wide range of species including cattle, horses, pigs, sheep, goats, dogs and cats.
This guide covers everything you need to know: how Shotapen LA works, correct dosages for each species, maximum injection volumes, what it treats, drug interactions to avoid, withdrawal periods, and the questions most commonly asked by farmers and pet owners.
What’s in Shotapen LA? (Active Ingredients)
Each 100 ml of Shotapen LA contains:
- Procaine benzylpenicillin – 10 g (rapid-acting penicillin, active for 18–24 hours)
- Benzathine benzylpenicillin – 10 g (slow-release penicillin, active for 3–5 days)
- Dihydrostreptomycin sulfate – 16.4 g (aminoglycoside, active for 72 hours)
The result is a suspension that achieves therapeutic antibiotic levels within 2 hours of injection and maintains them for a full 72 hours — hence the once-every-three-days dosing schedule.
How Does Shotapen LA Work?
Shotapen LA works through a two-pronged mechanism that covers both Gram-positive and Gram-negative bacteria:
Penicillin component: Benzylpenicillin inhibits the transpeptidase enzyme that bacteria need to cross-link the peptidoglycan chains in their cell walls. Without an intact cell wall, bacteria cannot maintain structural integrity and lyse (burst). This is a bactericidal (bacteria-killing) rather than bacteriostatic (bacteria-stopping) mechanism.
Dihydrostreptomycin component: This aminoglycoside binds to the 30S ribosome subunit of bacterial cells, causing misreading of mRNA and the incorporation of incorrect amino acids into proteins. This disrupts protein synthesis and is also bactericidal.
Crucially, these two mechanisms are synergistic: the cell wall disruption caused by penicillin enhances the penetration of dihydrostreptomycin into bacteria, making the combination more effective than either antibiotic alone and slowing the development of resistance.
What Bacteria Does Shotapen LA Kill?
Shotapen LA has a wide spectrum of activity:
- Gram-positive: Streptococcus spp., Staphylococcus spp., Clostridium spp., Erysipelothrix rhusiopathiae, Corynebacterium spp.
- Gram-negative: Pasteurella spp., Escherichia coli, Salmonella spp., Klebsiella spp., Haemophilus spp., Brucella spp., Campylobacter spp.
Shotapen LA Dosage Chart (By Species)
All doses are administered by intramuscular (IM) injection. Shake the bottle well before use. Repeat every 72 hours as required. Continue treatment for at least 48 hours after symptoms resolve.
| Animal | Dose per Injection | Example: 200 kg animal | Frequency |
|---|---|---|---|
| Cattle | 5–10 ml per 100 kg BW | 10–20 ml | Every 72 hours |
| Horses | 5–10 ml per 100 kg BW | 10–20 ml | Every 72 hours |
| Pigs (adult) | 5–10 ml per 100 kg BW | 5–10 ml (50 kg pig) | Every 72 hours |
| Calves | 1–2 ml per 25 kg BW | 4–8 ml (100 kg calf) | Every 72 hours |
| Foals | 1–2 ml per 25 kg BW | 4–8 ml (100 kg foal) | Every 72 hours |
| Piglets | 1–2 ml per 25 kg BW | 1–2 ml (25 kg piglet) | Every 72 hours |
| Sheep & Goats | 1–2 ml per 20 kg BW | 3–6 ml (60 kg sheep) | Every 72 hours |
| Dogs | 1–2 ml per 25 kg BW | 2–4 ml (50 kg dog) | Every 72 hours |
| Cats | 1–2 ml per 25 kg BW | 0.5–1 ml (6 kg cat) | Every 72 hours |
Maximum Volume Per Injection Site
When large doses are required, the injection volume must be split across multiple sites:
- Cattle and horses: maximum 20 ml per injection site
- Pigs: maximum 10 ml per injection site
- Calves and small ruminants: maximum 5 ml per injection site
What Does Shotapen LA Treat?
In Cattle
Shotapen LA is commonly used in cattle for: respiratory disease (pneumonia, shipping fever caused by Pasteurella multocida and Mannheimia haemolytica), septicemia, metritis, mastitis, leptospirosis, reticulo-peritonitis, and wound and postpartum infections.
In Pigs
In swine, Shotapen LA targets septicemia, MMA syndrome (mastitis-metritis-agalactia) in sows, erysipelas caused by Erysipelothrix rhusiopathiae, leptospirosis, and respiratory disease.
In Sheep & Goats
For small ruminants, Shotapen LA is used for vesicular stomatitis, arthritis, septicemia, clostridiasis, and wound infections.
In Horses
In horses, it is used for respiratory bacterial infections, wound infections, and postoperative antibiotic cover.
In Dogs & Cats
Shotapen LA can be used in dogs and cats for bacterial infections of the respiratory tract, urinary tract, musculoskeletal system, gastrointestinal tract, and skin wounds — where the causative organism is susceptible to benzylpenicillin and dihydrostreptomycin. It must not be used in rabbits or small rodents.
Withdrawal Periods
If animals are used for food production, observe these mandatory withdrawal periods after the last injection:
| Species | Meat / Slaughter Withdrawal | Milk Withdrawal |
|---|---|---|
| Cattle | 49 days | 5 days (10 milkings) |
| Pigs | 30–35 days | N/A |
Milk from dairy cows treated with Shotapen LA must not be used for human consumption during treatment or for 5 days (10 milkings) after the last injection. It can be given to animals after heat treatment during this period.
Drug Interactions to Avoid
Do not use Shotapen LA at the same time as the following antibiotics — the combinations can cause antagonism, treatment failure, or serious toxicity:
- Aminoglycosides with nephrotoxic/ototoxic effects: neomycin, kanamycin, gentamicin, monomycin (kidney and hearing damage risk)
- Macrolides: erythromycin, tylosin, tilmicosin
- Tetracyclines: oxytetracycline, doxycycline
- Polymyxins: polymyxin B, colistin
- Lincosamides: lincomycin, clindamycin
Storage Instructions
- Store in a dry, dark place at 15–25°C
- Can be refrigerated at 2–8°C for an 18-month shelf life (unopened)
- Unopened at 15–25°C: 12-month shelf life
- After first opening: use within 28 days (store at 5–25°C)
- Always shake well before use
Shotapen LA vs Other Long-Acting Antibiotics
| Feature | Shotapen LA | Betamox LA (Amoxicillin) | Draxxin (Tulathromycin) |
|---|---|---|---|
| Active ingredient(s) | Benzylpenicillin + Dihydrostreptomycin | Amoxicillin 150mg/ml | Tulathromycin 100mg/ml |
| Spectrum | Broad (G+ and G-) | Broad (G+ and G-) | Mainly respiratory pathogens |
| Duration of action | 72 hours | 48–72 hours | Up to 14 days (single dose) |
| Species | Cattle, horses, pigs, sheep, goats, dogs, cats | Cattle, pigs, sheep, dogs, cats | Cattle, pigs |
| Cattle meat withdrawal | 49 days | 21 days | 18 days |
| Best for | Multi-system infections, wide species range | Soft tissue, respiratory, urinary | Respiratory disease (BRD), single-dose convenience |
Where to Buy Shotapen LA
You can buy Shotapen LA Injectable Suspension 100ml online at PetShopBoss.com with free worldwide shipping. We carry the Virbac-manufactured 100ml vial at a competitive price with no prescription required for international orders.
Also available: Betamox LA Amoxicillin Injectable 100ml | Draxxin Injectable 100ml (Tulathromycin) | Tylosin Powder 50% 100g
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