Antimicrobial’s unique attributes explain efficacy against key SRD pathogens


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The efficacy of Draxxin® (tulathromycin) against key swine respiratory disease (SRD) pathogens is largely due to the antimicrobial’s ability to reach and sustain high concentrations in lung tissue, says Lucina Galina, DVM, PhD, director of swine technical services, Zoetis.

Draxxin was the first antimicrobial in a macrolide class known as triamilides. It’s a semisynthetic derivative of erythromycin developed by Zoetis scientists exclusively for veterinary use, Galina says.

This unique antimicrobial is administered as a single intramuscular (IM) injection for the treatment of SRD associated with Actinobacillus pleuropneumoniae (APP), Pasteurella multocida (PM), Bordetella bronchiseptica, Haemophilus parasuis and Mycoplasma hyopneumoniae (M. hyo). The dosage is 2.5 mg/kg bodyweight. It’s also indicated at the same dosage for the control of SRD associated with APP, PM and M. hyo in groups of pigs where SRD has been diagnosed.

The antimicrobial’s mode of activity is similar to other macrolides. It selectively binds to a large subunit of ribosomes known as 50S. Ribosomes build proteins, and the product’s binding action inhibits bacterial protein synthesis.

Highly bioavailable

Draxxin has several beneficial attributes that have been demonstrated in studies, according to Galina.

The antimicrobial is rapidly released from the IM injection site. It takes only 15 minutes for Draxxin to reach maximum plasma concentrations. “Draxxin is also an impressive 88% bioavailable,”1 she says.

When investigators sampled lungs as well as blood after IM administration of Draxxin, they found it was extensively distributed to lung tissues. “In fact, the AUC was more than 61 times greater for the lung than for plasma. AUC stands for ‘area under the curve’ and is a measure of the drug in plasma based on drug concentration and time,”2 Galina reports.

Accumulates in immune cells

“One of the antimicrobial’s most powerful attributes is its accumulation in immune cells, specifically alveolar macrophages and neutrophils.3 These are phagocytic white blood cells that are part of the immune system and fight off bacteria,” she says.

Another important characteristic is the product’s slow elimination. “The elimination half-life of Draxxin in the lungs is 6 days.That means it takes 6 days for the amount of the drug in the body to be reduced by half. That’s a very long half-life and helps prolong the drug at the site of infection,” Galina says.

“These attributes explain the antimicrobial’s efficacy against key SRD pathogens and why one injection of the antimicrobial enables pork producers to reduce mortality from SRD, reduce the need for re-treatment and improve weight gain among affected pigs,”5 she says.


Important Safety Information for Swine: The pre-slaughter withdrawal time for DRAXXIN in swine is 5 days. DRAXXIN should not be used in animals known to be hypersensitive to the product.  Click here to see prescribing information for Draxxin.

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1 Benchaoui HA, et al. Pharmacokinetics and lung tissue concentrations of tulathromycin in swine. J Vet Pharmacol Ther. 2004;27:203-210.
2 Ibid.
3 Fischer CD, et al. Direct and Indirect Anti-Inflammatory Effects of Tulathromycin in Bovine Macrophages: Inhibition of CXCL-8 Secretion, Induction of Apoptosis, and Promotion of Efferocytosis. Antimicrob Agents Chemother. 2013 March ;57(3):1385-1393.
4 Benchaoui HA, et al. Pharmacokinetics and lung tissue concentrations of tulathromycin in swine. J Vet Pharmacol Ther. 2004;27:203-210.
5 King D, et al. Effects of DRAXXIN at Weaning for Control of Swine Respiratory Disease in Pigs Experiencing a Natural Outbreak. In Proceedings, American Association of Swine Veterinarians 45th Annual Meeting. 207-214. 2014.


Discoveries is a series of  research news reports written by the editors of Pig Health Today on behalf of the US Pork Business of Zoetis.


October 2021