Dufamox 15% L.A. Amoxicillin Injection: Dosage Guide for Cattle, Sheep,

Dufamox 15% L.A. is one of the most commonly used injectable amoxicillin formulations in livestock veterinary practice. Manufactured by Dutch Farm International, it delivers 150mg of amoxicillin trihydrate per ml in a long-acting oily suspension that maintains therapeutic antibiotic concentrations for 48 hours from a single injection — halving the number of treatments required compared to standard aqueous amoxicillin formulations.

This guide covers everything you need: how the long-acting formula works, the correct dose for each species, withdrawal periods for dairy cattle, which drug combinations to avoid, and when Dufamox is the right choice versus a potentiated amoxicillin product like Synulox.

What Is Dufamox 15% L.A. and How Does It Work?

Dufamox 15% L.A. contains amoxicillin trihydrate 150mg/ml (15% w/v) suspended in a sterile oily vehicle. Amoxicillin is a semi-synthetic aminopenicillin — a member of the beta-lactam antibiotic family — that kills bacteria by blocking two enzymes (transpeptidase and carboxypeptidase) that bacteria need to build and maintain their cell walls. Without intact cell walls, bacteria cannot survive the osmotic pressure of their environment and die during the growth phase. This makes amoxicillin bactericidal (bacteria-killing) rather than merely bacteriostatic (bacteria-stopping).

The “L.A.” (Long-Acting) designation refers to the oily suspension vehicle. Standard amoxicillin aqueous injections are rapidly absorbed and cleared, requiring once or twice daily dosing. In Dufamox 15% L.A., micronised (very finely ground) amoxicillin trihydrate particles are suspended in an oily matrix that forms a slow-release depot at the intramuscular injection site. Amoxicillin is gradually released from this depot over 48 hours, maintaining therapeutic blood and tissue concentrations throughout. This means a single injection every 48 hours is sufficient rather than daily treatment.

Which Bacteria Does Dufamox 15% Target?

Amoxicillin has broad-spectrum activity across both Gram-positive and Gram-negative pathogens:

Gram-positive: Streptococcus spp., Staphylococcus spp. (penicillinase-negative only), Clostridium spp., Corynebacterium spp., Erysipelothrix rhusiopathiae, Listeria monocytogenes, Bacillus anthracis, Actinomyces spp.
Gram-negative: E. coli, Pasteurella spp., Haemophilus spp., Salmonella spp., Proteus mirabilis, Moraxella spp., Fusobacterium spp., Campylobacter spp.

Critical limitation: Amoxicillin is destroyed by beta-lactamase enzymes produced by certain bacteria (including resistant Staphylococcus, Klebsiella, Enterobacter and Pseudomonas). Dufamox will be ineffective against these organisms. In cases where beta-lactamase-producing bacteria are suspected — particularly in chronic, recurrent, or previously-treated infections in dogs and cats — a potentiated amoxicillin product combining amoxicillin with clavulanic acid (such as Synulox RTU or Clavaseptin) is the correct choice.

What Infections Does Dufamox 15% L.A. Treat?

Dufamox is indicated for bacterial infections across multiple body systems in cattle, sheep, goats, pigs, dogs and cats:

Respiratory: pneumonia, bronchopneumonia, bronchitis, rhinitis, tracheitis, pharyngitis
Gastrointestinal: enteritis, gastroenteritis, diarrhoea of bacterial origin
Genitourinary: metritis, endometritis, cystitis, urethritis, pyelonephritis
Mammary: mastitis in cattle and agalactia in sows
Skin and soft tissue: wounds, abscesses, joint infections, pyoderma, umbilical infections
Specific diseases: leptospirosis, erysipelas in pigs, actinomycosis in cattle, paratyphoid fever

Dufamox 15% L.A. Dosage Chart

The standard dose for all species is 1 ml per 10 kg body weight, equivalent to 15 mg amoxicillin per kg. Give by IM injection in livestock; IM or SC in dogs and cats. Repeat every 48 hours. Treat for 3–5 days; maximum 7 days. Always shake the vial vigorously before use to resuspend the settlement. Use sterile, dry syringes only — moisture degrades the suspension. Massage the injection site gently after administration.

Animal	Dose	Example Calculation	Route	Frequency
Adult cattle	1 ml / 10 kg	500 kg cow = 50 ml (split across sites)	IM	Every 48h
Calves	1 ml / 10 kg	100 kg calf = 10 ml	IM	Every 48h
Sheep & Goats	1 ml / 10 kg	60 kg ewe = 6 ml	IM	Every 48h
Pigs	1 ml / 10 kg	100 kg finisher = 10 ml	IM	Every 48h
Dogs	1 ml / 10 kg	30 kg dog = 3 ml	IM or SC	Every 48h
Cats	1 ml / 10 kg	5 kg cat = 0.5 ml	IM or SC	Every 48h

Maximum Injection Site Volumes

To avoid tissue damage and discomfort, do not exceed these volumes at a single injection site. Split larger doses across multiple muscle groups:

Cattle: 20 ml maximum per site
Pigs: 10 ml maximum per site
Sheep, goats, calves: 5 ml maximum per site

Withdrawal Periods — Critical for Food-Producing Animals

Species	Meat & Offal	Milk
Cattle	14 days after last injection	60 hours (5 milkings) after last injection
Sheep & Goats	14 days after last injection	Not for use in dairy sheep/goats producing milk for human consumption
Pigs	14 days after last injection	N/A

The 60-hour milk withdrawal for dairy cattle (5 milkings at 12-hour intervals) is relatively short compared to many other antibiotic injectables — making Dufamox a practical choice for treating mastitis and other infections in milking cows. Always verify withdrawal periods against the product label authorised in your country, as they can vary by market.

Drug Combinations to Avoid

This is one of the most commonly overlooked aspects of amoxicillin use. Bactericidal antibiotics like amoxicillin work by attacking actively dividing bacteria. Bacteriostatic antibiotics stop bacterial division. Combining the two is counterproductive — bacteriostatic drugs prevent the bacterial growth that amoxicillin needs to be effective. The following combinations are pharmacologically antagonistic:

Tetracyclines (oxytetracycline, doxycycline) — do not combine
Chloramphenicol — do not combine
Macrolides (tylosin, erythromycin, tilmicosin) — do not combine
Lincosamides (lincomycin, clindamycin) — do not combine
Sulfonamides — do not combine

Additionally, do not mix Dufamox with other drugs in the same syringe, and do not combine with novobiocin or B vitamins (pharmaceutical incompatibility).

Contraindications — When NOT to Use Dufamox

Penicillin or beta-lactam allergy: do not use in animals with known hypersensitivity
Rabbits, guinea pigs, hamsters, gerbils: aminopenicillins cause fatal disruption of the hindgut microbiome in these species — never use amoxicillin in them
Intravenous administration: never give IV — the oily suspension is for IM/SC use only
Penicillinase-producing infections: ineffective against beta-lactamase-producing bacteria; use a clavulanate-potentiated product instead
Severe renal impairment: dose adjustment required; amoxicillin is primarily renally excreted
Ruminants: avoid prolonged courses (beyond 5–7 days) as extended use can destabilise ruminal microflora

Dufamox 15% vs Synulox RTU — Which Should You Use?

Both contain amoxicillin, but there is one critical difference. Synulox RTU adds clavulanic acid, which inhibits the beta-lactamase enzymes that resistant bacteria produce to destroy penicillin. This makes Synulox effective against beta-lactamase-producing strains that Dufamox cannot treat.

Use Dufamox 15% L.A. when: the infecting organism is known or highly likely to be amoxicillin-susceptible; for straightforward first-line treatment of respiratory, gastrointestinal, or genitourinary infections in livestock where culture and sensitivity isn’t available but the clinical context suggests a susceptible pathogen; for cattle mastitis and metritis.
Use Synulox RTU when: beta-lactamase-producing organisms are suspected; in dogs and cats with skin/wound infections, urinary tract infections, or oral infections where resistant Staphylococci are common; in cases that have failed to respond to plain amoxicillin treatment.

Where to Buy Dufamox 15% L.A.

You can order Dufamox 15% L.A. Amoxicillin Injectable Suspension from PetShopBoss.com with free worldwide shipping. No prescription required for international orders.

Dufamox 15% L.A. Amoxicillin Injection: Dosage Guide for Cattle, Sheep, Pigs, Dogs & Cats – Withdrawal Periods, Drug Interactions & When to Use It