Selected Antimicrobial Information – Equine

Clarithromycin [Equine]

Restriction Status



Species Usage Dose

For treatment of Rhodococcus equi in foals 5mg/kg PO q12h (extra-label use)
For treatment of Lawsonia intracellularis in foals 7.5mg/kg PO q12h (extra-label use)

Brand Name(s)



Clarithromycin is a bacteriostatic, time-dependent macrolide antibiotic with broad-spectrum activity against Gram-positive aerobes and some Gram-negative aerobes, such as the Pasteurellaceae. Clarithromycin is not effective against Pseudomonas aeruginosa, and many Enterobacteriaceae have acquired resistance. Clarithromycin is bactericidal against Streptococcus spp. It is widely distributed, including into abscesses, and can be used to treat intracellular organisms. Excretion is primarily in bile.

Acceptable Uses

  • Used in combination with rifampin for treatment of Rhodococcus equi pneumonia in foals.

Unacceptable Uses

  • N/A

Formulations Available within the OSU Pharmacy

  • Clarithromycin 500mg tablet


  • Severe and fatal colitis has been associated with macrolide use in adult horses and thus should be avoided in adults. Foals receiving treatment with a macrolide antibiotic should have their mouths rinsed out after to administration to prevent adverse effects to the mare.
  • Macrolides have been associated with significant hyperthermia in treated foals due to off-target effects on apocrine sweat glands; treated foals should not be housed in direct sunlight for prolonged periods of time and should have access to a climate-controlled enclosure.


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OSU VMC Antimicrobial Use Guidelines Copyright © 2018 by The Ohio State University College of Veterinary Medicine is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.