Selected Antimicrobial Information – Equine

Rifampin [Equine]

Restriction Status



Species Usage Dose

For treatment of Rhodococcus equi 5mg/kg PO q12h (to be used in combination with a macrolide antibiotic) (extra-label use)
For treatment of susceptible infections 10mg/kg PO q24h (to be used in combination with another antibiotic) (extra-label use)

Brand Name(s)



Rifampin is a bactericidal, concentration-dependent antibiotic with a narrow spectrum of activity against Gram-positive aerobes, some non-enteric Gram-negative aerobes, and most anaerobes. Distribution is wide, including intracellularly, and rifampin remains active in acidic environments such as necrotic tissue. Excretion is not fully understood, but is thought to be primarily in bile.

Acceptable Uses

  • Used in combination with a macrolide, for treatment of Rhodococcus equi pneumonia in foals.
  • Used in combination with penicillin, ceftiofur, or potentiated sulfonamides, for treatment of internal abscesses caused by Corynebacterium spp. or Streptococcus spp.
  • Treatment of mycobacterial infections.
  • Treatment of penicillinase-producing Staphylococcus aureus infections.

Unacceptable Uses

  • Rifampin should never be used as the sole antimicrobial for treating a patient due to rapid development of resistance; it should always be used in conjunction with another antibiotic.
  • Antagonized by concurrent use of fluoroquinolones.

Formulations Available within the OSU Pharmacy

  • Rifampin 300mg capsule


  • May affect elimination of other hepatically-metabolized drugs (e.g. barbiturates, xylazine).
  • Causes orange to red staining of urine, mucous membranes, and other secretions.


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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.