Selected Antimicrobial Information – Companion Animal

Azithromycin [Companion]

Restriction Status



Species Usage Dose

For respiratory infections associated with Mycoplasma 5-15mg/kg PO q24h for 5d, then q72h for 6-8wks (extra-label use)
For other bacterial infections
7-15mg/kg PO q12h for 5-7d (extra-label use)
For toxoplasmosis 10mg/kg PO q24h for 4wks (would not be first choice-see Clindamycin) (extra-label use)

For susceptible infections 5-10mg/kg PO q24h for 3-7d (up to 10-20d for skin infections) (extra-label use)
For Babesia 10-11.6mg/kg PO q24h for 10d, given in combination with atovaquone (extra-label use)
For Giardia
5mg/kg PO q24h for 5d (Would not be first choice. Note there are no drugs approved for the treatment of giardiasis in dogs and cats in the USA.) (extra-label use)

Brand Name(s)



Azithromycin is a bacteriostatic, time-dependent macrolide antibiotic. It has activity against some Gram-positive aerobes as Staphylococcus spp., and some Gram-negative aerobes, such as Bordetella bronchiseptica. It is also active against many spirochetes and intracellular organisms, though there are exceptions (see Unacceptable Uses). Azithromycin is not effective against Pseudomonas aeruginosa, and many Enterobacteriaceae have acquired resistance. It is widely distributed, and can be used in the presence of necrotic tissue. Excretion is primarily in bile.

Acceptable Uses

  • Treatment of systemic infections.
  • Treatment of bacterial upper respiratory infection in cats associated with Mycoplasma spp.
  • Treatment of some protozoal infections, such as Babesia spp., Giardia spp., Cryptosporidium spp., or Toxoplasma gondii.

Unacceptable Uses

  • Cats with hemotropic mycoplasmas (e.g. Mycoplasma haemofelis) or Chlamydophila felis infections will not clear infection after treatment with azithromycin.

Formulations Available within the OSU Pharmacy

  • Azithromycin 20mg/ml oral suspension
  • Azithromycin 250mg tablet


  • Gastrointestinal adverse effects are less severe compared to erythromycin, which acts as a potent prokinetic agent.


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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.