Selected Antimicrobial Information – Companion Animal

Cephalexin [Companion]

Restriction Status



Species Usage Dose

For soft tissue infections 15-30mg/kg PO q12h for 14-28d (extra-label use)
For systemic infections
35mg/kg PO q6-8h for 14-28d if indicated by culture/susceptibility (extra-label use)

Label dose 22mg/kg PO q12h for up to 28d
For pyoderma 22-35mg/kg PO q12h
For respiratory tract infections 20-40mg/kg PO q8h for 7-14d if indicated by culture/susceptibility (extra-label use)
For systemic infections
25-45mg/kg PO q8h for 14-28d if indicated by culture/susceptibility (extra-label)
For orthopedic infections 22-30mg/kg PO q6-8h for 28d (extra-label)
For urinary tract infections 15mg/kg PO q6-8h for 14-28d (extra-label)

Brand Name(s)

Rilexine®, Keflex®


Cephalexin is a bactericidal, time-dependent first generation cephalosporin (β-lactam) antibiotic with activity primarily against Gram-positive aerobes, and more limited activity against Gram-negative aerobes and anaerobes. Cephalexin is not effective against Enterococcus spp., Pseudomonas aeruginosa, and methicillin-resistant Staphylococcus spp. Distribution throughout the body is wide, including into bone, but cephalexin does not penetrate intracellularly or cross the blood-brain barrier. Excretion is primarily in urine and bile.

Acceptable Uses

  • First line empiric treatment of pyoderma associated with susceptible Staphylococcus spp. Culture/susceptibility are recommended if not a first-time infection.
  • Treatment of other susceptible soft tissue infections.
  • Less preferred treatment for urinary tract infections.

Unacceptable Uses

  • N/A

Formulations Available within the OSU Pharmacy

  • Cephalexin 250mg capsule
  • Cephalexin 500mg capsule
  • Cephalexin 50mg/ml oral suspension


  • N/A


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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.